diff --git a/include/nlohmann/detail/input/input_adapters.hpp b/include/nlohmann/detail/input/input_adapters.hpp
index 0a108476..ed9db0f6 100644
--- a/include/nlohmann/detail/input/input_adapters.hpp
+++ b/include/nlohmann/detail/input/input_adapters.hpp
@@ -247,15 +247,15 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
             }
             else if (wc <= 0x7FF)
             {
-                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((wc >> 6u)));
-                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (wc & 0x3Fu));
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((static_cast<unsigned int>(wc) >> 6u)));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
                 utf8_bytes_filled = 2;
             }
             else if (0xD800 > wc or wc >= 0xE000)
             {
-                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((wc >> 12u)));
-                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((wc >> 6u) & 0x3Fu));
-                utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (wc & 0x3Fu));
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((static_cast<unsigned int>(wc) >> 12u)));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
+                utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
                 utf8_bytes_filled = 3;
             }
             else
@@ -263,7 +263,7 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
                 if (JSON_HEDLEY_UNLIKELY(not input.empty()))
                 {
                     const auto wc2 = static_cast<unsigned int>(input.get_character());
-                    const auto charcode = 0x10000u + (((wc & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
+                    const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
                     utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
                     utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
                     utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
@@ -339,15 +339,18 @@ struct iterator_input_adapter_factory
     }
 };
 
-// This test breaks astyle formatting when inlined in a template specialization.
 template<typename T>
-inline constexpr bool is_iterator_of_multibyte()
+struct is_iterator_of_multibyte
 {
-    return sizeof(typename std::iterator_traits<T>::value_type) > 1;
-}
+    using value_type = typename std::iterator_traits<T>::value_type;
+    enum
+    {
+        value = sizeof(value_type) > 1
+    };
+};
 
 template<typename IteratorType>
-struct iterator_input_adapter_factory<IteratorType, enable_if_t<is_iterator_of_multibyte<IteratorType>()>>
+struct iterator_input_adapter_factory<IteratorType, enable_if_t<is_iterator_of_multibyte<IteratorType>::value>>
 {
     using iterator_type = IteratorType;
     using char_type = typename std::iterator_traits<iterator_type>::value_type;
diff --git a/include/nlohmann/detail/input/lexer.hpp b/include/nlohmann/detail/input/lexer.hpp
index e710140b..0ff0c736 100644
--- a/include/nlohmann/detail/input/lexer.hpp
+++ b/include/nlohmann/detail/input/lexer.hpp
@@ -113,7 +113,7 @@ class lexer : public lexer_base<BasicJsonType>
     using token_type = typename lexer_base<BasicJsonType>::token_type;
 
     explicit lexer(InputAdapterType&& adapter)
-        : ia(std::move(adapter)), decimal_point_char(static_cast<char_type>(get_decimal_point())) {}
+        : ia(std::move(adapter)), decimal_point_char(static_cast<char_int_type>(get_decimal_point())) {}
 
     // delete because of pointer members
     lexer(const lexer&) = delete;
@@ -1218,7 +1218,7 @@ scan_number_done:
     token_type scan_literal(const char_type* literal_text, const std::size_t length,
                             token_type return_type)
     {
-        assert(current == literal_text[0]);
+        assert(std::char_traits<char_type>::to_char_type(current) == literal_text[0]);
         for (std::size_t i = 1; i < length; ++i)
         {
             if (JSON_HEDLEY_UNLIKELY(std::char_traits<char_type>::to_char_type(get()) != literal_text[i]))
@@ -1523,7 +1523,7 @@ scan_number_done:
     number_float_t value_float = 0;
 
     /// the decimal point
-    const char_type decimal_point_char = '.';
+    const char_int_type decimal_point_char = '.';
 };
 }  // namespace detail
 }  // namespace nlohmann
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index dd9b21c4..e45a756f 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -4669,15 +4669,15 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
             }
             else if (wc <= 0x7FF)
             {
-                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((wc >> 6u)));
-                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (wc & 0x3Fu));
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xC0u | ((static_cast<unsigned int>(wc) >> 6u)));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
                 utf8_bytes_filled = 2;
             }
             else if (0xD800 > wc or wc >= 0xE000)
             {
-                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((wc >> 12u)));
-                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((wc >> 6u) & 0x3Fu));
-                utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (wc & 0x3Fu));
+                utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xE0u | ((static_cast<unsigned int>(wc) >> 12u)));
+                utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((static_cast<unsigned int>(wc) >> 6u) & 0x3Fu));
+                utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | (static_cast<unsigned int>(wc) & 0x3Fu));
                 utf8_bytes_filled = 3;
             }
             else
@@ -4685,7 +4685,7 @@ struct wide_string_input_helper<BaseInputAdapter, 2>
                 if (JSON_HEDLEY_UNLIKELY(not input.empty()))
                 {
                     const auto wc2 = static_cast<unsigned int>(input.get_character());
-                    const auto charcode = 0x10000u + (((wc & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
+                    const auto charcode = 0x10000u + (((static_cast<unsigned int>(wc) & 0x3FFu) << 10u) | (wc2 & 0x3FFu));
                     utf8_bytes[0] = static_cast<std::char_traits<char>::int_type>(0xF0u | (charcode >> 18u));
                     utf8_bytes[1] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 12u) & 0x3Fu));
                     utf8_bytes[2] = static_cast<std::char_traits<char>::int_type>(0x80u | ((charcode >> 6u) & 0x3Fu));
@@ -4761,15 +4761,18 @@ struct iterator_input_adapter_factory
     }
 };
 
-// This test breaks astyle formatting when inlined in a template specialization.
 template<typename T>
-inline constexpr bool is_iterator_of_multibyte()
+struct is_iterator_of_multibyte
 {
-    return sizeof(typename std::iterator_traits<T>::value_type) > 1;
-}
+    using value_type = typename std::iterator_traits<T>::value_type;
+    enum
+    {
+        value = sizeof(value_type) > 1
+    };
+};
 
 template<typename IteratorType>
-struct iterator_input_adapter_factory<IteratorType, enable_if_t<is_iterator_of_multibyte<IteratorType>()>>
+struct iterator_input_adapter_factory<IteratorType, enable_if_t<is_iterator_of_multibyte<IteratorType>::value>>
 {
     using iterator_type = IteratorType;
     using char_type = typename std::iterator_traits<iterator_type>::value_type;
@@ -8177,7 +8180,7 @@ class lexer : public lexer_base<BasicJsonType>
     using token_type = typename lexer_base<BasicJsonType>::token_type;
 
     explicit lexer(InputAdapterType&& adapter)
-        : ia(std::move(adapter)), decimal_point_char(static_cast<char_type>(get_decimal_point())) {}
+        : ia(std::move(adapter)), decimal_point_char(static_cast<char_int_type>(get_decimal_point())) {}
 
     // delete because of pointer members
     lexer(const lexer&) = delete;
@@ -9282,7 +9285,7 @@ scan_number_done:
     token_type scan_literal(const char_type* literal_text, const std::size_t length,
                             token_type return_type)
     {
-        assert(current == literal_text[0]);
+        assert(std::char_traits<char_type>::to_char_type(current) == literal_text[0]);
         for (std::size_t i = 1; i < length; ++i)
         {
             if (JSON_HEDLEY_UNLIKELY(std::char_traits<char_type>::to_char_type(get()) != literal_text[i]))
@@ -9587,7 +9590,7 @@ scan_number_done:
     number_float_t value_float = 0;
 
     /// the decimal point
-    const char_type decimal_point_char = '.';
+    const char_int_type decimal_point_char = '.';
 };
 }  // namespace detail
 }  // namespace nlohmann
diff --git a/test/src/unit-deserialization.cpp b/test/src/unit-deserialization.cpp
index 15744b9e..88b1f3c5 100644
--- a/test/src/unit-deserialization.cpp
+++ b/test/src/unit-deserialization.cpp
@@ -1039,3 +1039,60 @@ TEST_CASE("deserialization")
         }));
     }
 }
+
+TEST_CASE_TEMPLATE("deserialization of different character types (ASCII)", T,
+                   char, unsigned char, signed char,
+                   wchar_t,
+                   char16_t, char32_t,
+                   std::uint8_t, std::int8_t,
+                   std::int16_t, std::uint16_t,
+                   std::int32_t, std::uint32_t)
+{
+    std::vector<T> v = {'t', 'r', 'u', 'e'};
+    CHECK(json::parse(v) == json(true));
+    CHECK(json::accept(v));
+
+    SaxEventLogger l;
+    CHECK(json::sax_parse(v, &l));
+    CHECK(l.events.size() == 1);
+    CHECK(l.events == std::vector<std::string>({"boolean(true)"}));
+}
+
+TEST_CASE_TEMPLATE("deserialization of different character types (UTF-8)", T,
+                   char, unsigned char, std::uint8_t)
+{
+    // a star emoji
+    std::vector<T> v = {'"', static_cast<T>(0xe2), static_cast<T>(0xad), static_cast<T>(0x90), static_cast<T>(0xef), static_cast<T>(0xb8), static_cast<T>(0x8f), '"'};
+    CHECK(json::parse(v).dump(-1, ' ', true) == "\"\\u2b50\\ufe0f\"");
+    CHECK(json::accept(v));
+
+    SaxEventLogger l;
+    CHECK(json::sax_parse(v, &l));
+    CHECK(l.events.size() == 1);
+}
+
+TEST_CASE_TEMPLATE("deserialization of different character types (UTF-16)", T,
+                   char16_t, std::uint16_t)
+{
+    // a star emoji
+    std::vector<T> v = {static_cast<T>('"'), static_cast<T>(0x2b50), static_cast<T>(0xfe0f), static_cast<T>('"')};
+    CHECK(json::parse(v).dump(-1, ' ', true) == "\"\\u2b50\\ufe0f\"");
+    CHECK(json::accept(v));
+
+    SaxEventLogger l;
+    CHECK(json::sax_parse(v, &l));
+    CHECK(l.events.size() == 1);
+}
+
+TEST_CASE_TEMPLATE("deserialization of different character types (UTF-32)", T,
+                   char32_t, std::uint32_t)
+{
+    // a star emoji
+    std::vector<T> v = {static_cast<T>('"'), static_cast<T>(0x2b50), static_cast<T>(0xfe0f), static_cast<T>('"')};
+    CHECK(json::parse(v).dump(-1, ' ', true) == "\"\\u2b50\\ufe0f\"");
+    CHECK(json::accept(v));
+
+    SaxEventLogger l;
+    CHECK(json::sax_parse(v, &l));
+    CHECK(l.events.size() == 1);
+}