diff --git a/src/json.hpp b/src/json.hpp
index 7f6e2a7a..88266699 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -6262,44 +6262,36 @@ class basic_json
         }
     }
 
-    template<typename T>
-    static T get_from_vector(const std::vector<uint8_t>& vec, size_t bytes, size_t current_idx)
+    template<typename T, typename std::enable_if<sizeof(T) == 1, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
     {
-        assert(bytes == 1 or bytes == 2 or bytes == 4 or bytes == 8);
-
-        switch (bytes)
-        {
-            case 1:
-            {
-                return static_cast<T>(vec[current_idx + 1]);
-            }
-
-            case 2:
-            {
-                return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 010) +
-                                      static_cast<T>(vec[current_idx + 2]));
-            }
-
-            case 4:
-            {
-                return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 030) +
-                                      (static_cast<T>(vec[current_idx + 2]) << 020) +
-                                      (static_cast<T>(vec[current_idx + 3]) << 010) +
-                                      static_cast<T>(vec[current_idx + 4]));
-            }
-
-            case 8:
-            {
-                return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 070) +
-                                      (static_cast<T>(vec[current_idx + 2]) << 060) +
-                                      (static_cast<T>(vec[current_idx + 3]) << 050) +
-                                      (static_cast<T>(vec[current_idx + 4]) << 040) +
-                                      (static_cast<T>(vec[current_idx + 5]) << 030) +
-                                      (static_cast<T>(vec[current_idx + 6]) << 020) +
-                                      (static_cast<T>(vec[current_idx + 7]) << 010) +
-                                      static_cast<T>(vec[current_idx + 8]));
-            }
-        }
+        return static_cast<T>(vec[current_idx + 1]);
+    }
+    template<typename T, typename std::enable_if<sizeof(T) == 2, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
+    {
+        return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 010) +
+                              static_cast<T>(vec[current_idx + 2]));
+    }
+    template<typename T, typename std::enable_if<sizeof(T) == 4, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
+    {
+        return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 030) +
+                              (static_cast<T>(vec[current_idx + 2]) << 020) +
+                              (static_cast<T>(vec[current_idx + 3]) << 010) +
+                              static_cast<T>(vec[current_idx + 4]));
+    }
+    template<typename T, typename std::enable_if<sizeof(T) == 8, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
+    {
+        return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 070) +
+                              (static_cast<T>(vec[current_idx + 2]) << 060) +
+                              (static_cast<T>(vec[current_idx + 3]) << 050) +
+                              (static_cast<T>(vec[current_idx + 4]) << 040) +
+                              (static_cast<T>(vec[current_idx + 5]) << 030) +
+                              (static_cast<T>(vec[current_idx + 6]) << 020) +
+                              (static_cast<T>(vec[current_idx + 7]) << 010) +
+                              static_cast<T>(vec[current_idx + 8]));
     }
 
     static void to_msgpack_internal(const basic_json& j, std::vector<uint8_t>& v)
@@ -6847,42 +6839,42 @@ class basic_json
         else if (v[current_idx] == 0xcc) // uint 8
         {
             idx += 1; // skip content byte
-            return get_from_vector<uint8_t>(v, 1, current_idx);
+            return get_from_vector<uint8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xcd) // uint 16
         {
             idx += 2; // skip 2 content bytes
-            return get_from_vector<uint16_t>(v, 2, current_idx);
+            return get_from_vector<uint16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xce) // uint 32
         {
             idx += 4; // skip 4 content bytes
-            return get_from_vector<uint32_t>(v, 4, current_idx);
+            return get_from_vector<uint32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xcf) // uint 64
         {
             idx += 8; // skip 8 content bytes
-            return get_from_vector<uint64_t>(v, 8, current_idx);
+            return get_from_vector<uint64_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd0) // int 8
         {
             idx += 1; // skip content byte
-            return get_from_vector<int8_t>(v, 1, current_idx);
+            return get_from_vector<int8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd1) // int 16
         {
             idx += 2; // skip 2 content bytes
-            return get_from_vector<int16_t>(v, 2, current_idx);
+            return get_from_vector<int16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd2) // int 32
         {
             idx += 4; // skip 4 content bytes
-            return get_from_vector<int32_t>(v, 4, current_idx);
+            return get_from_vector<int32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd3) // int 64
         {
             idx += 8; // skip 8 content bytes
-            return get_from_vector<int64_t>(v, 8, current_idx);
+            return get_from_vector<int64_t>(v, current_idx);
         }
         else if (v[current_idx] >= 0xd4 and v[current_idx] <= 0xd8) // fixext
         {
@@ -6890,21 +6882,21 @@ class basic_json
         }
         else if (v[current_idx] == 0xd9) // str 8
         {
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             const size_t offset = current_idx + 2;
             idx += len + 1; // skip size byte + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0xda) // str 16
         {
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             const size_t offset = current_idx + 3;
             idx += len + 2; // skip 2 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0xdb) // str 32
         {
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             const size_t offset = current_idx + 5;
             idx += len + 4; // skip 4 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
@@ -6912,7 +6904,7 @@ class basic_json
         else if (v[current_idx] == 0xdc) // array 16
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 2 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6923,7 +6915,7 @@ class basic_json
         else if (v[current_idx] == 0xdd) // array 32
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6934,7 +6926,7 @@ class basic_json
         else if (v[current_idx] == 0xde) // map 16
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 2 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6946,7 +6938,7 @@ class basic_json
         else if (v[current_idx] == 0xdf) // map 32
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6975,22 +6967,22 @@ class basic_json
         else if (v[current_idx] == 0x18) // Unsigned integer uint8_t
         {
             idx += 1; // skip content byte
-            return get_from_vector<uint8_t>(v, 1, current_idx);
+            return get_from_vector<uint8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x19) // Unsigned integer uint16_t
         {
             idx += 2; // skip 2 content bytes
-            return get_from_vector<uint16_t>(v, 2, current_idx);
+            return get_from_vector<uint16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x1a) // Unsigned integer uint32_t
         {
             idx += 4; // skip 4 content bytes
-            return get_from_vector<uint32_t>(v, 4, current_idx);
+            return get_from_vector<uint32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x1b) // Unsigned integer uint64_t
         {
             idx += 8; // skip 8 content bytes
-            return get_from_vector<uint64_t>(v, 8, current_idx);
+            return get_from_vector<uint64_t>(v, current_idx);
         }
         else if (v[current_idx] >= 0x20 and v[current_idx] <= 0x37) // Negative integer
         {
@@ -6999,23 +6991,23 @@ class basic_json
         else if (v[current_idx] == 0x38) // Negative integer
         {
             idx += 1; // skip content byte
-            // must be int64_t !
-            return -1 - get_from_vector<int16_t>(v, 1, current_idx);
+            // must be uint8_t !
+            return -1 - get_from_vector<uint8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x39) // Negative integer
         {
             idx += 2; // skip 2 content bytes
-            return -1 - get_from_vector<int16_t>(v, 2, current_idx);
+            return -1 - get_from_vector<int16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x3a) // Negative integer
         {
             idx += 4; // skip 4 content bytes
-            return -1 - get_from_vector<int32_t>(v, 4, current_idx);
+            return -1 - get_from_vector<int32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x3b) // Negative integer
         {
             idx += 8; // skip 8 content bytes
-            return -1 - get_from_vector<int64_t>(v, 8, current_idx);
+            return -1 - get_from_vector<int64_t>(v, current_idx);
         }
         else if (v[current_idx] >= 0x60 and v[current_idx] <= 0x77) // UTF-8 string
         {
@@ -7026,28 +7018,28 @@ class basic_json
         }
         else if (v[current_idx] == 0x78) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             const size_t offset = current_idx + 2;
             idx += len + 1; // skip size byte + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0x79) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             const size_t offset = current_idx + 3;
             idx += len + 2; // skip 2 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0x7a) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             const size_t offset = current_idx + 5;
             idx += len + 4; // skip 4 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0x7b) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 8, current_idx);
+            const auto len = get_from_vector<uint64_t>(v, current_idx);
             const size_t offset = current_idx + 9;
             idx += len + 8; // skip 8 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
@@ -7065,7 +7057,7 @@ class basic_json
         else if (v[current_idx] == 0x98) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             idx += 1; // skip 1 size byte
             for (size_t i = 0; i < len; ++i)
             {
@@ -7076,7 +7068,7 @@ class basic_json
         else if (v[current_idx] == 0x99) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7087,7 +7079,7 @@ class basic_json
         else if (v[current_idx] == 0x9a) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7098,7 +7090,7 @@ class basic_json
         else if (v[current_idx] == 0x9b) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 8, current_idx);
+            const auto len = get_from_vector<uint64_t>(v, current_idx);
             idx += 8; // skip 8 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7120,7 +7112,7 @@ class basic_json
         else if (v[current_idx] == 0xb8) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             idx += 1; // skip 1 size byte
             for (size_t i = 0; i < len; ++i)
             {
@@ -7132,7 +7124,7 @@ class basic_json
         else if (v[current_idx] == 0xb9) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 2 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7144,7 +7136,7 @@ class basic_json
         else if (v[current_idx] == 0xba) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7156,7 +7148,7 @@ class basic_json
         else if (v[current_idx] == 0xbb) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 8, current_idx);
+            const auto len = get_from_vector<uint64_t>(v, current_idx);
             idx += 8; // skip 8 size bytes
             for (size_t i = 0; i < len; ++i)
             {
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index 7daf9c49..027218ee 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -6262,44 +6262,36 @@ class basic_json
         }
     }
 
-    template<typename T>
-    static T get_from_vector(const std::vector<uint8_t>& vec, size_t bytes, size_t current_idx)
+    template<typename T, typename std::enable_if<sizeof(T) == 1, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
     {
-        assert(bytes == 1 or bytes == 2 or bytes == 4 or bytes == 8);
-
-        switch (bytes)
-        {
-            case 1:
-            {
-                return static_cast<T>(vec[current_idx + 1]);
-            }
-
-            case 2:
-            {
-                return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 010) +
-                                      static_cast<T>(vec[current_idx + 2]));
-            }
-
-            case 4:
-            {
-                return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 030) +
-                                      (static_cast<T>(vec[current_idx + 2]) << 020) +
-                                      (static_cast<T>(vec[current_idx + 3]) << 010) +
-                                      static_cast<T>(vec[current_idx + 4]));
-            }
-
-            case 8:
-            {
-                return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 070) +
-                                      (static_cast<T>(vec[current_idx + 2]) << 060) +
-                                      (static_cast<T>(vec[current_idx + 3]) << 050) +
-                                      (static_cast<T>(vec[current_idx + 4]) << 040) +
-                                      (static_cast<T>(vec[current_idx + 5]) << 030) +
-                                      (static_cast<T>(vec[current_idx + 6]) << 020) +
-                                      (static_cast<T>(vec[current_idx + 7]) << 010) +
-                                      static_cast<T>(vec[current_idx + 8]));
-            }
-        }
+        return static_cast<T>(vec[current_idx + 1]);
+    }
+    template<typename T, typename std::enable_if<sizeof(T) == 2, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
+    {
+        return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 010) +
+                              static_cast<T>(vec[current_idx + 2]));
+    }
+    template<typename T, typename std::enable_if<sizeof(T) == 4, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
+    {
+        return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 030) +
+                              (static_cast<T>(vec[current_idx + 2]) << 020) +
+                              (static_cast<T>(vec[current_idx + 3]) << 010) +
+                              static_cast<T>(vec[current_idx + 4]));
+    }
+    template<typename T, typename std::enable_if<sizeof(T) == 8, int>::type = 0>
+    static constexpr T get_from_vector(const std::vector<uint8_t>& vec, const size_t current_idx)
+    {
+        return static_cast<T>((static_cast<T>(vec[current_idx + 1]) << 070) +
+                              (static_cast<T>(vec[current_idx + 2]) << 060) +
+                              (static_cast<T>(vec[current_idx + 3]) << 050) +
+                              (static_cast<T>(vec[current_idx + 4]) << 040) +
+                              (static_cast<T>(vec[current_idx + 5]) << 030) +
+                              (static_cast<T>(vec[current_idx + 6]) << 020) +
+                              (static_cast<T>(vec[current_idx + 7]) << 010) +
+                              static_cast<T>(vec[current_idx + 8]));
     }
 
     static void to_msgpack_internal(const basic_json& j, std::vector<uint8_t>& v)
@@ -6847,42 +6839,42 @@ class basic_json
         else if (v[current_idx] == 0xcc) // uint 8
         {
             idx += 1; // skip content byte
-            return get_from_vector<uint8_t>(v, 1, current_idx);
+            return get_from_vector<uint8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xcd) // uint 16
         {
             idx += 2; // skip 2 content bytes
-            return get_from_vector<uint16_t>(v, 2, current_idx);
+            return get_from_vector<uint16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xce) // uint 32
         {
             idx += 4; // skip 4 content bytes
-            return get_from_vector<uint32_t>(v, 4, current_idx);
+            return get_from_vector<uint32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xcf) // uint 64
         {
             idx += 8; // skip 8 content bytes
-            return get_from_vector<uint64_t>(v, 8, current_idx);
+            return get_from_vector<uint64_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd0) // int 8
         {
             idx += 1; // skip content byte
-            return get_from_vector<int8_t>(v, 1, current_idx);
+            return get_from_vector<int8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd1) // int 16
         {
             idx += 2; // skip 2 content bytes
-            return get_from_vector<int16_t>(v, 2, current_idx);
+            return get_from_vector<int16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd2) // int 32
         {
             idx += 4; // skip 4 content bytes
-            return get_from_vector<int32_t>(v, 4, current_idx);
+            return get_from_vector<int32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0xd3) // int 64
         {
             idx += 8; // skip 8 content bytes
-            return get_from_vector<int64_t>(v, 8, current_idx);
+            return get_from_vector<int64_t>(v, current_idx);
         }
         else if (v[current_idx] >= 0xd4 and v[current_idx] <= 0xd8) // fixext
         {
@@ -6890,21 +6882,21 @@ class basic_json
         }
         else if (v[current_idx] == 0xd9) // str 8
         {
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             const size_t offset = current_idx + 2;
             idx += len + 1; // skip size byte + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0xda) // str 16
         {
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             const size_t offset = current_idx + 3;
             idx += len + 2; // skip 2 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0xdb) // str 32
         {
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             const size_t offset = current_idx + 5;
             idx += len + 4; // skip 4 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
@@ -6912,7 +6904,7 @@ class basic_json
         else if (v[current_idx] == 0xdc) // array 16
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 2 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6923,7 +6915,7 @@ class basic_json
         else if (v[current_idx] == 0xdd) // array 32
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6934,7 +6926,7 @@ class basic_json
         else if (v[current_idx] == 0xde) // map 16
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 2 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6946,7 +6938,7 @@ class basic_json
         else if (v[current_idx] == 0xdf) // map 32
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -6975,22 +6967,22 @@ class basic_json
         else if (v[current_idx] == 0x18) // Unsigned integer uint8_t
         {
             idx += 1; // skip content byte
-            return get_from_vector<uint8_t>(v, 1, current_idx);
+            return get_from_vector<uint8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x19) // Unsigned integer uint16_t
         {
             idx += 2; // skip 2 content bytes
-            return get_from_vector<uint16_t>(v, 2, current_idx);
+            return get_from_vector<uint16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x1a) // Unsigned integer uint32_t
         {
             idx += 4; // skip 4 content bytes
-            return get_from_vector<uint32_t>(v, 4, current_idx);
+            return get_from_vector<uint32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x1b) // Unsigned integer uint64_t
         {
             idx += 8; // skip 8 content bytes
-            return get_from_vector<uint64_t>(v, 8, current_idx);
+            return get_from_vector<uint64_t>(v, current_idx);
         }
         else if (v[current_idx] >= 0x20 and v[current_idx] <= 0x37) // Negative integer
         {
@@ -6999,23 +6991,23 @@ class basic_json
         else if (v[current_idx] == 0x38) // Negative integer
         {
             idx += 1; // skip content byte
-            // must be int64_t !
-            return -1 - get_from_vector<int16_t>(v, 1, current_idx);
+            // must be uint8_t !
+            return -1 - get_from_vector<uint8_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x39) // Negative integer
         {
             idx += 2; // skip 2 content bytes
-            return -1 - get_from_vector<int16_t>(v, 2, current_idx);
+            return -1 - get_from_vector<int16_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x3a) // Negative integer
         {
             idx += 4; // skip 4 content bytes
-            return -1 - get_from_vector<int32_t>(v, 4, current_idx);
+            return -1 - get_from_vector<int32_t>(v, current_idx);
         }
         else if (v[current_idx] == 0x3b) // Negative integer
         {
             idx += 8; // skip 8 content bytes
-            return -1 - get_from_vector<int64_t>(v, 8, current_idx);
+            return -1 - get_from_vector<int64_t>(v, current_idx);
         }
         else if (v[current_idx] >= 0x60 and v[current_idx] <= 0x77) // UTF-8 string
         {
@@ -7026,28 +7018,28 @@ class basic_json
         }
         else if (v[current_idx] == 0x78) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             const size_t offset = current_idx + 2;
             idx += len + 1; // skip size byte + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0x79) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             const size_t offset = current_idx + 3;
             idx += len + 2; // skip 2 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0x7a) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             const size_t offset = current_idx + 5;
             idx += len + 4; // skip 4 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
         }
         else if (v[current_idx] == 0x7b) // UTF-8 string
         {
-            const size_t len = get_from_vector<size_t>(v, 8, current_idx);
+            const auto len = get_from_vector<uint64_t>(v, current_idx);
             const size_t offset = current_idx + 9;
             idx += len + 8; // skip 8 size bytes + content bytes
             return std::string(reinterpret_cast<const char*>(v.data()) + offset, len);
@@ -7065,7 +7057,7 @@ class basic_json
         else if (v[current_idx] == 0x98) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             idx += 1; // skip 1 size byte
             for (size_t i = 0; i < len; ++i)
             {
@@ -7076,7 +7068,7 @@ class basic_json
         else if (v[current_idx] == 0x99) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7087,7 +7079,7 @@ class basic_json
         else if (v[current_idx] == 0x9a) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7098,7 +7090,7 @@ class basic_json
         else if (v[current_idx] == 0x9b) // array
         {
             basic_json result = value_t::array;
-            const size_t len = get_from_vector<size_t>(v, 8, current_idx);
+            const auto len = get_from_vector<uint64_t>(v, current_idx);
             idx += 8; // skip 8 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7120,7 +7112,7 @@ class basic_json
         else if (v[current_idx] == 0xb8) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 1, current_idx);
+            const auto len = get_from_vector<uint8_t>(v, current_idx);
             idx += 1; // skip 1 size byte
             for (size_t i = 0; i < len; ++i)
             {
@@ -7132,7 +7124,7 @@ class basic_json
         else if (v[current_idx] == 0xb9) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 2, current_idx);
+            const auto len = get_from_vector<uint16_t>(v, current_idx);
             idx += 2; // skip 2 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7144,7 +7136,7 @@ class basic_json
         else if (v[current_idx] == 0xba) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 4, current_idx);
+            const auto len = get_from_vector<uint32_t>(v, current_idx);
             idx += 4; // skip 4 size bytes
             for (size_t i = 0; i < len; ++i)
             {
@@ -7156,7 +7148,7 @@ class basic_json
         else if (v[current_idx] == 0xbb) // map
         {
             basic_json result = value_t::object;
-            const size_t len = get_from_vector<size_t>(v, 8, current_idx);
+            const auto len = get_from_vector<uint64_t>(v, current_idx);
             idx += 8; // skip 8 size bytes
             for (size_t i = 0; i < len; ++i)
             {