diff --git a/doc/mkdocs/docs/features/macros.md b/doc/mkdocs/docs/features/macros.md
index 8b10ef1f3..bf279a139 100644
--- a/doc/mkdocs/docs/features/macros.md
+++ b/doc/mkdocs/docs/features/macros.md
@@ -24,6 +24,13 @@ The diagnostics messages can also be controlled with the CMake option `JSON_Diag
 
 The library targets C++11, but also supports some features introduced in later C++ versions (e.g., `std::string_view` support for C++17). For these new features, the library implements some preprocessor checks to determine the C++ standard. By defining any of these symbols, the internal check is overridden and the provided C++ version is unconditionally assumed. This can be helpful for compilers that only implement parts of the standard and would be detected incorrectly.
 
+## `JSON_HAS_FILESYSTEM`, `JSON_HAS_EXPERIMENTAL_FILESYSTEM`
+
+When compiling with C++17, the library provides conversions from and to `std::filesystem::path`. As compiler support
+for filesystem is limited, the library tries to detect whether `<filesystem>`/`std::filesystem` (`JSON_HAS_FILESYSTEM`)
+or `<experimental/filesystem>`/`std::experimental::filesystem` (`JSON_HAS_EXPERIMENTAL_FILESYSTEM`) should be used.
+To override the built-in check, define `JSON_HAS_FILESYSTEM` or `JSON_HAS_EXPERIMENTAL_FILESYSTEM` to `1`.
+
 ## `JSON_NOEXCEPTION`
 
 Exceptions can be switched off by defining the symbol `JSON_NOEXCEPTION`.
diff --git a/include/nlohmann/detail/macro_scope.hpp b/include/nlohmann/detail/macro_scope.hpp
index 00f197b63..83d8e06b4 100644
--- a/include/nlohmann/detail/macro_scope.hpp
+++ b/include/nlohmann/detail/macro_scope.hpp
@@ -37,23 +37,25 @@
     #define JSON_HAS_CPP_11
 #endif
 
-#ifdef JSON_HAS_CPP_17
-    #if defined(__cpp_lib_filesystem)
-        #define JSON_HAS_FILESYSTEM 1
-    #elif defined(__cpp_lib_experimental_filesystem)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #elif !defined(__has_include)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #elif __has_include(<filesystem>)
-        #define JSON_HAS_FILESYSTEM 1
-    #elif __has_include(<experimental/filesystem>)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #endif
+#if !defined(JSON_HAS_FILESYSTEM) && !defined(JSON_HAS_EXPERIMENTAL_FILESYSTEM)
+    #ifdef JSON_HAS_CPP_17
+        #if defined(__cpp_lib_filesystem)
+            #define JSON_HAS_FILESYSTEM 1
+        #elif defined(__cpp_lib_experimental_filesystem)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #elif !defined(__has_include)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #elif __has_include(<filesystem>)
+            #define JSON_HAS_FILESYSTEM 1
+        #elif __has_include(<experimental/filesystem>)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #endif
 
-    // std::filesystem does not work on MinGW GCC 8: https://sourceforge.net/p/mingw-w64/bugs/737/
-    #if defined(__MINGW32__) && defined(__GNUC__) && __GNUC__ == 8
-        #undef JSON_HAS_FILESYSTEM
-        #undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
+        // std::filesystem does not work on MinGW GCC 8: https://sourceforge.net/p/mingw-w64/bugs/737/
+        #if defined(__MINGW32__) && defined(__GNUC__) && __GNUC__ == 8
+            #undef JSON_HAS_FILESYSTEM
+            #undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
+        #endif
     #endif
 #endif
 
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index ae187d1fd..5be8bfa5d 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -2325,23 +2325,25 @@ using is_detected_convertible =
     #define JSON_HAS_CPP_11
 #endif
 
-#ifdef JSON_HAS_CPP_17
-    #if defined(__cpp_lib_filesystem)
-        #define JSON_HAS_FILESYSTEM 1
-    #elif defined(__cpp_lib_experimental_filesystem)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #elif !defined(__has_include)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #elif __has_include(<filesystem>)
-        #define JSON_HAS_FILESYSTEM 1
-    #elif __has_include(<experimental/filesystem>)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #endif
+#if !defined(JSON_HAS_FILESYSTEM) && !defined(JSON_HAS_EXPERIMENTAL_FILESYSTEM)
+    #ifdef JSON_HAS_CPP_17
+        #if defined(__cpp_lib_filesystem)
+            #define JSON_HAS_FILESYSTEM 1
+        #elif defined(__cpp_lib_experimental_filesystem)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #elif !defined(__has_include)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #elif __has_include(<filesystem>)
+            #define JSON_HAS_FILESYSTEM 1
+        #elif __has_include(<experimental/filesystem>)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #endif
 
-    // std::filesystem does not work on MinGW GCC 8: https://sourceforge.net/p/mingw-w64/bugs/737/
-    #if defined(__MINGW32__) && defined(__GNUC__) && __GNUC__ == 8
-        #undef JSON_HAS_FILESYSTEM
-        #undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
+        // std::filesystem does not work on MinGW GCC 8: https://sourceforge.net/p/mingw-w64/bugs/737/
+        #if defined(__MINGW32__) && defined(__GNUC__) && __GNUC__ == 8
+            #undef JSON_HAS_FILESYSTEM
+            #undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
+        #endif
     #endif
 #endif
 
diff --git a/test/src/unit-regression2.cpp b/test/src/unit-regression2.cpp
index 237d8e904..22c0154d3 100644
--- a/test/src/unit-regression2.cpp
+++ b/test/src/unit-regression2.cpp
@@ -49,25 +49,35 @@ using ordered_json = nlohmann::ordered_json;
 #ifdef JSON_HAS_CPP_17
     #include <variant>
 
-    #if defined(__cpp_lib_filesystem)
-        #define JSON_HAS_FILESYSTEM 1
-    #elif defined(__cpp_lib_experimental_filesystem)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #elif !defined(__has_include)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #elif __has_include(<filesystem>)
-        #define JSON_HAS_FILESYSTEM 1
-    #elif __has_include(<experimental/filesystem>)
-        #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
-    #endif
+    #if !defined(JSON_HAS_FILESYSTEM) && !defined(JSON_HAS_EXPERIMENTAL_FILESYSTEM)
+        #if defined(__cpp_lib_filesystem)
+            #define JSON_HAS_FILESYSTEM 1
+        #elif defined(__cpp_lib_experimental_filesystem)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #elif !defined(__has_include)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #elif __has_include(<filesystem>)
+            #define JSON_HAS_FILESYSTEM 1
+        #elif __has_include(<experimental/filesystem>)
+            #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
+        #endif
 
-    // std::filesystem does not work on MinGW GCC 8: https://sourceforge.net/p/mingw-w64/bugs/737/
-    #if defined(__MINGW32__) && defined(__GNUC__) && __GNUC__ == 8
-        #undef JSON_HAS_FILESYSTEM
-        #undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
+        // std::filesystem does not work on MinGW GCC 8: https://sourceforge.net/p/mingw-w64/bugs/737/
+        #if defined(__MINGW32__) && defined(__GNUC__) && __GNUC__ == 8
+            #undef JSON_HAS_FILESYSTEM
+            #undef JSON_HAS_EXPERIMENTAL_FILESYSTEM
+        #endif
     #endif
 #endif
 
+#ifndef JSON_HAS_EXPERIMENTAL_FILESYSTEM
+    #define JSON_HAS_EXPERIMENTAL_FILESYSTEM 0
+#endif
+
+#ifndef JSON_HAS_FILESYSTEM
+    #define JSON_HAS_FILESYSTEM 0
+#endif
+
 #if JSON_HAS_EXPERIMENTAL_FILESYSTEM
 #include <experimental/filesystem>
 namespace nlohmann::detail