diff --git a/include/nlohmann/detail/input/binary_reader.hpp b/include/nlohmann/detail/input/binary_reader.hpp
index 27c34edb..19aae087 100644
--- a/include/nlohmann/detail/input/binary_reader.hpp
+++ b/include/nlohmann/detail/input/binary_reader.hpp
@@ -1560,7 +1560,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_array(-1)))
+            if (JSON_UNLIKELY(not sax->start_array(std::size_t(-1))))
             {
                 return false;
             }
@@ -1630,7 +1630,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_object(-1)))
+            if (JSON_UNLIKELY(not sax->start_object(std::size_t(-1))))
             {
                 return false;
             }
diff --git a/include/nlohmann/detail/input/json_sax.hpp b/include/nlohmann/detail/input/json_sax.hpp
index fe1cf7c5..2a2e6011 100644
--- a/include/nlohmann/detail/input/json_sax.hpp
+++ b/include/nlohmann/detail/input/json_sax.hpp
@@ -190,7 +190,7 @@ class json_sax_dom_parser
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
 
-        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive object size: " + std::to_string(len)));
@@ -216,7 +216,7 @@ class json_sax_dom_parser
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
 
-        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive array size: " + std::to_string(len)));
@@ -373,7 +373,7 @@ class json_sax_dom_callback_parser
         // check object limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive object size: " + std::to_string(len)));
@@ -446,7 +446,7 @@ class json_sax_dom_callback_parser
         // check array limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive array size: " + std::to_string(len)));
@@ -649,7 +649,7 @@ class json_sax_acceptor
         return true;
     }
 
-    bool start_object(std::size_t = -1)
+    bool start_object(std::size_t = std::size_t(-1))
     {
         return true;
     }
@@ -664,7 +664,7 @@ class json_sax_acceptor
         return true;
     }
 
-    bool start_array(std::size_t = -1)
+    bool start_array(std::size_t = std::size_t(-1))
     {
         return true;
     }
diff --git a/include/nlohmann/detail/input/parser.hpp b/include/nlohmann/detail/input/parser.hpp
index cfb8b65e..70d92a26 100644
--- a/include/nlohmann/detail/input/parser.hpp
+++ b/include/nlohmann/detail/input/parser.hpp
@@ -146,7 +146,7 @@ class parser
     template <typename SAX>
     bool sax_parse(SAX* sax, const bool strict = true)
     {
-        (void)detail::is_sax_static_asserts<SAX, BasicJsonType>{};
+        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
         const bool result = sax_parse_internal(sax);
 
         // strict mode: next byte must be EOF
@@ -179,7 +179,7 @@ class parser
                 {
                     case token_type::begin_object:
                     {
-                        if (JSON_UNLIKELY(not sax->start_object(-1)))
+                        if (JSON_UNLIKELY(not sax->start_object(std::size_t(-1))))
                         {
                             return false;
                         }
@@ -227,7 +227,7 @@ class parser
 
                     case token_type::begin_array:
                     {
-                        if (JSON_UNLIKELY(not sax->start_array(-1)))
+                        if (JSON_UNLIKELY(not sax->start_array(std::size_t(-1))))
                         {
                             return false;
                         }
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 2e73d98f..dacdcfbf 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -3966,7 +3966,7 @@ class json_sax_dom_parser
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::object));
 
-        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive object size: " + std::to_string(len)));
@@ -3992,7 +3992,7 @@ class json_sax_dom_parser
     {
         ref_stack.push_back(handle_value(BasicJsonType::value_t::array));
 
-        if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+        if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
         {
             JSON_THROW(out_of_range::create(408,
                                             "excessive array size: " + std::to_string(len)));
@@ -4149,7 +4149,7 @@ class json_sax_dom_callback_parser
         // check object limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive object size: " + std::to_string(len)));
@@ -4222,7 +4222,7 @@ class json_sax_dom_callback_parser
         // check array limit
         if (ref_stack.back())
         {
-            if (JSON_UNLIKELY(len != -1 and len > ref_stack.back()->max_size()))
+            if (JSON_UNLIKELY(len != std::size_t(-1) and len > ref_stack.back()->max_size()))
             {
                 JSON_THROW(out_of_range::create(408,
                                                 "excessive array size: " + std::to_string(len)));
@@ -4425,7 +4425,7 @@ class json_sax_acceptor
         return true;
     }
 
-    bool start_object(std::size_t = -1)
+    bool start_object(std::size_t = std::size_t(-1))
     {
         return true;
     }
@@ -4440,7 +4440,7 @@ class json_sax_acceptor
         return true;
     }
 
-    bool start_array(std::size_t = -1)
+    bool start_array(std::size_t = std::size_t(-1))
     {
         return true;
     }
@@ -4595,7 +4595,7 @@ class parser
     template <typename SAX>
     bool sax_parse(SAX* sax, const bool strict = true)
     {
-        // (void)detail::is_sax_static_asserts<SAX, BasicJsonType>{};
+        (void)detail::is_sax_static_asserts<SAX, BasicJsonType> {};
         const bool result = sax_parse_internal(sax);
 
         // strict mode: next byte must be EOF
@@ -4628,7 +4628,7 @@ class parser
                 {
                     case token_type::begin_object:
                     {
-                        if (JSON_UNLIKELY(not sax->start_object(-1)))
+                        if (JSON_UNLIKELY(not sax->start_object(std::size_t(-1))))
                         {
                             return false;
                         }
@@ -4676,7 +4676,7 @@ class parser
 
                     case token_type::begin_array:
                     {
-                        if (JSON_UNLIKELY(not sax->start_array(-1)))
+                        if (JSON_UNLIKELY(not sax->start_array(std::size_t(-1))))
                         {
                             return false;
                         }
@@ -7515,7 +7515,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_array(-1)))
+            if (JSON_UNLIKELY(not sax->start_array(std::size_t(-1))))
             {
                 return false;
             }
@@ -7585,7 +7585,7 @@ class binary_reader
         }
         else
         {
-            if (JSON_UNLIKELY(not sax->start_object(-1)))
+            if (JSON_UNLIKELY(not sax->start_object(std::size_t(-1))))
             {
                 return false;
             }
diff --git a/test/src/unit-conversions.cpp b/test/src/unit-conversions.cpp
index 787897ca..bf6332ff 100644
--- a/test/src/unit-conversions.cpp
+++ b/test/src/unit-conversions.cpp
@@ -435,7 +435,7 @@ TEST_CASE("value conversion")
 
     SECTION("get null (explicit)")
     {
-        std::nullptr_t n;
+        std::nullptr_t n = nullptr;
         json j(n);
 
         auto n2 = j.get<std::nullptr_t>();
diff --git a/test/src/unit-deserialization.cpp b/test/src/unit-deserialization.cpp
index e122628e..af58a0fe 100644
--- a/test/src/unit-deserialization.cpp
+++ b/test/src/unit-deserialization.cpp
@@ -35,45 +35,45 @@ using nlohmann::json;
 #include <iostream>
 #include <valarray>
 
-struct SaxEventLogger
+struct SaxEventLogger : public nlohmann::json_sax<json>
 {
-    bool null()
+    bool null() override
     {
         events.push_back("null()");
         return true;
     }
 
-    bool boolean(bool val)
+    bool boolean(bool val) override
     {
         events.push_back(val ? "boolean(true)" : "boolean(false)");
         return true;
     }
 
-    bool number_integer(json::number_integer_t val)
+    bool number_integer(json::number_integer_t val) override
     {
         events.push_back("number_integer(" + std::to_string(val) + ")");
         return true;
     }
 
-    bool number_unsigned(json::number_unsigned_t val)
+    bool number_unsigned(json::number_unsigned_t val) override
     {
         events.push_back("number_unsigned(" + std::to_string(val) + ")");
         return true;
     }
 
-    bool number_float(json::number_float_t, const std::string& s)
+    bool number_float(json::number_float_t, const std::string& s) override
     {
         events.push_back("number_float(" + s + ")");
         return true;
     }
 
-    bool string(std::string& val)
+    bool string(std::string& val) override
     {
         events.push_back("string(" + val + ")");
         return true;
     }
 
-    bool start_object(std::size_t elements)
+    bool start_object(std::size_t elements) override
     {
         if (elements == std::size_t(-1))
         {
@@ -86,19 +86,19 @@ struct SaxEventLogger
         return true;
     }
 
-    bool key(std::string& val)
+    bool key(std::string& val) override
     {
         events.push_back("key(" + val + ")");
         return true;
     }
 
-    bool end_object()
+    bool end_object() override
     {
         events.push_back("end_object()");
         return true;
     }
 
-    bool start_array(std::size_t elements)
+    bool start_array(std::size_t elements) override
     {
         if (elements == std::size_t(-1))
         {
@@ -111,13 +111,13 @@ struct SaxEventLogger
         return true;
     }
 
-    bool end_array()
+    bool end_array() override
     {
         events.push_back("end_array()");
         return true;
     }
 
-    bool parse_error(std::size_t position, const std::string&, const json::exception&)
+    bool parse_error(std::size_t position, const std::string&, const json::exception&) override
     {
         events.push_back("parse_error(" + std::to_string(position) + ")");
         return false;
@@ -128,9 +128,9 @@ struct SaxEventLogger
 
 struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger
 {
-    bool start_object(std::size_t elements)
+    bool start_object(std::size_t elements) override
     {
-        if (elements == -1)
+        if (elements == std::size_t(-1))
         {
             events.push_back("start_object()");
         }
@@ -144,7 +144,7 @@ struct SaxEventLoggerExitAfterStartObject : public SaxEventLogger
 
 struct SaxEventLoggerExitAfterKey : public SaxEventLogger
 {
-    bool key(std::string& val)
+    bool key(std::string& val) override
     {
         events.push_back("key(" + val + ")");
         return false;
@@ -153,9 +153,9 @@ struct SaxEventLoggerExitAfterKey : public SaxEventLogger
 
 struct SaxEventLoggerExitAfterStartArray : public SaxEventLogger
 {
-    bool start_array(std::size_t elements)
+    bool start_array(std::size_t elements) override
     {
-        if (elements == -1)
+        if (elements == std::size_t(-1))
         {
             events.push_back("start_array()");
         }
diff --git a/test/src/unit-inspection.cpp b/test/src/unit-inspection.cpp
index e50c7338..4c03cf96 100644
--- a/test/src/unit-inspection.cpp
+++ b/test/src/unit-inspection.cpp
@@ -317,8 +317,8 @@ TEST_CASE("object inspection")
     SECTION("round trips")
     {
         for (const auto& s :
-    {"3.141592653589793", "1000000000000000010E5"
-    })
+                {"3.141592653589793", "1000000000000000010E5"
+                })
         {
             json j1 = json::parse(s);
             std::string s1 = j1.dump();