diff --git a/src/json.hpp b/src/json.hpp
index ce2fb44e..6a6cbb85 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -62,7 +62,7 @@ SOFTWARE.
     #if (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__) < 30400
         #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
     #endif
-#elif defined(__GNUC__)
+#elif defined(__GNUC__) && !(defined(__ICC) || defined(__INTEL_COMPILER))
     #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40900
         #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
     #endif
@@ -6320,7 +6320,7 @@ class serializer
     */
     static constexpr std::size_t bytes_following(const uint8_t u)
     {
-        return ((0 <= u and u <= 127) ? 0
+        return ((u <= 127) ? 0
                 : ((192 <= u and u <= 223) ? 1
                    : ((224 <= u and u <= 239) ? 2
                       : ((240 <= u and u <= 247) ? 3 : std::string::npos))));
@@ -6660,7 +6660,7 @@ class serializer
             return;
         }
 
-        const bool is_negative = x < 0;
+        const auto is_negative = std::signbit(x);
         std::size_t i = 0;
 
         // spare 1 byte for '\0'
@@ -9759,7 +9759,7 @@ class basic_json
             , "incompatible pointer type");
 
         // delegate the call to get_impl_ptr<>() const
-        return get_impl_ptr(static_cast<const PointerType>(nullptr));
+        return get_impl_ptr(static_cast<PointerType>(nullptr));
     }
 
     /*!
diff --git a/test/src/unit-cbor.cpp b/test/src/unit-cbor.cpp
index 4ec03f23..02f3d482 100644
--- a/test/src/unit-cbor.cpp
+++ b/test/src/unit-cbor.cpp
@@ -739,13 +739,13 @@ TEST_CASE("CBOR")
                 {
                     SECTION("no byte follows")
                     {
-                        CHECK_THROWS_AS(json::from_cbor(std::vector<uint8_t>({0xf9})), json::parse_error);
+                        CHECK_THROWS_AS(json::from_cbor(std::vector<uint8_t>({0xf9})), json::parse_error&);
                         CHECK_THROWS_WITH(json::from_cbor(std::vector<uint8_t>({0xf9})),
                                           "[json.exception.parse_error.110] parse error at 2: unexpected end of input");
                     }
                     SECTION("only one byte follows")
                     {
-                        CHECK_THROWS_AS(json::from_cbor(std::vector<uint8_t>({0xf9, 0x7c})), json::parse_error);
+                        CHECK_THROWS_AS(json::from_cbor(std::vector<uint8_t>({0xf9, 0x7c})), json::parse_error&);
                         CHECK_THROWS_WITH(json::from_cbor(std::vector<uint8_t>({0xf9, 0x7c})),
                                           "[json.exception.parse_error.110] parse error at 3: unexpected end of input");
                     }
diff --git a/test/src/unit-deserialization.cpp b/test/src/unit-deserialization.cpp
index 9f574807..2798f102 100644
--- a/test/src/unit-deserialization.cpp
+++ b/test/src/unit-deserialization.cpp
@@ -451,11 +451,11 @@ TEST_CASE("deserialization")
 
         SECTION("BOM only")
         {
-            CHECK_THROWS_AS(json::parse(bom), json::parse_error);
+            CHECK_THROWS_AS(json::parse(bom), json::parse_error&);
             CHECK_THROWS_WITH(json::parse(bom),
                               "[json.exception.parse_error.101] parse error at 1: syntax error - unexpected end of input; expected '[', '{', or a literal");
 
-            CHECK_THROWS_AS(json::parse(std::istringstream(bom)), json::parse_error);
+            CHECK_THROWS_AS(json::parse(std::istringstream(bom)), json::parse_error&);
             CHECK_THROWS_WITH(json::parse(std::istringstream(bom)),
                               "[json.exception.parse_error.101] parse error at 1: syntax error - unexpected end of input; expected '[', '{', or a literal");
         }
@@ -468,22 +468,22 @@ TEST_CASE("deserialization")
 
         SECTION("2 byte of BOM")
         {
-            CHECK_THROWS_AS(json::parse(bom.substr(0, 2)), json::parse_error);
+            CHECK_THROWS_AS(json::parse(bom.substr(0, 2)), json::parse_error&);
             CHECK_THROWS_WITH(json::parse(bom),
                               "[json.exception.parse_error.101] parse error at 1: syntax error - unexpected end of input; expected '[', '{', or a literal");
 
-            CHECK_THROWS_AS(json::parse(std::istringstream(bom.substr(0, 2))), json::parse_error);
+            CHECK_THROWS_AS(json::parse(std::istringstream(bom.substr(0, 2))), json::parse_error&);
             CHECK_THROWS_WITH(json::parse(std::istringstream(bom)),
                               "[json.exception.parse_error.101] parse error at 1: syntax error - unexpected end of input; expected '[', '{', or a literal");
         }
 
         SECTION("1 byte of BOM")
         {
-            CHECK_THROWS_AS(json::parse(bom.substr(0, 1)), json::parse_error);
+            CHECK_THROWS_AS(json::parse(bom.substr(0, 1)), json::parse_error&);
             CHECK_THROWS_WITH(json::parse(bom),
                               "[json.exception.parse_error.101] parse error at 1: syntax error - unexpected end of input; expected '[', '{', or a literal");
 
-            CHECK_THROWS_AS(json::parse(std::istringstream(bom.substr(0, 1))), json::parse_error);
+            CHECK_THROWS_AS(json::parse(std::istringstream(bom.substr(0, 1))), json::parse_error&);
             CHECK_THROWS_WITH(json::parse(std::istringstream(bom)),
                               "[json.exception.parse_error.101] parse error at 1: syntax error - unexpected end of input; expected '[', '{', or a literal");
         }
@@ -504,9 +504,9 @@ TEST_CASE("deserialization")
                         CAPTURE(i2);
 
                         std::string s = "";
-                        s.push_back(bom[0] + i0);
-                        s.push_back(bom[1] + i1);
-                        s.push_back(bom[2] + i2);
+                        s.push_back(static_cast<char>(bom[0] + i0));
+                        s.push_back(static_cast<char>(bom[1] + i1));
+                        s.push_back(static_cast<char>(bom[2] + i2));
 
                         if (i0 == 0 and i1 == 0 and i2 == 0)
                         {
@@ -517,8 +517,8 @@ TEST_CASE("deserialization")
                         else
                         {
                             // any variation is an error
-                            CHECK_THROWS_AS(json::parse(s + "null"), json::parse_error);
-                            CHECK_THROWS_AS(json::parse(std::istringstream(s + "null")), json::parse_error);
+                            CHECK_THROWS_AS(json::parse(s + "null"), json::parse_error&);
+                            CHECK_THROWS_AS(json::parse(std::istringstream(s + "null")), json::parse_error&);
                         }
                     }
                 }