diff --git a/CMakeLists.txt b/CMakeLists.txt
index f2da77d24e..ec1140f367 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,6 +32,7 @@ if(WIN32)
 		message(STATUS "Using 3rd party repository")
 	endif()
 	set(USE_MSYSTEM ${_msystem} CACHE INTERNAL "Use MSYS2 subsystem")
+	set(HAVE_MSYSTEM ${USE_MSYSTEM}) # For config.h
 	set(USE_REPOSITORY ${_repository} CACHE INTERNAL "Use Wireshark 3rd Party Repository")
 endif()
 
diff --git a/cmakeconfig.h.in b/cmakeconfig.h.in
index bd4c64e004..817da33692 100644
--- a/cmakeconfig.h.in
+++ b/cmakeconfig.h.in
@@ -309,6 +309,9 @@
 /* Define to 1 if the 'ssize_t' type exists. */
 #cmakedefine HAVE_SSIZE_T 1
 
+/* Define to 1 if we are using the msys2 environment to build. */
+#cmakedefine HAVE_MSYSTEM 1
+
 #if defined(_MSC_VER)
 #  define strncasecmp strnicmp
 #  define popen       _popen
diff --git a/ui/qt/main.cpp b/ui/qt/main.cpp
index b551032ad5..cb46c110fd 100644
--- a/ui/qt/main.cpp
+++ b/ui/qt/main.cpp
@@ -342,7 +342,7 @@ check_and_warn_user_startup()
 }
 #endif
 
-#if defined(_WIN32) && !defined(__MINGW64__)
+#if defined(_WIN32) && !defined(HAVE_MSYSTEM)
 // Try to avoid library search path collisions. QCoreApplication will
 // search QT_INSTALL_PREFIX/plugins for platform DLLs before searching
 // the application directory. If
@@ -650,7 +650,7 @@ int main(int argc, char *qt_argv[])
 
     commandline_early_options(argc, argv);
 
-#if defined(_WIN32) && !defined(__MINGW64__)
+#if defined(_WIN32) && !defined(HAVE_MSYSTEM)
     win32_reset_library_path();
 #endif
 
diff --git a/wsutil/filesystem.c b/wsutil/filesystem.c
index 79052de219..909aecd86e 100644
--- a/wsutil/filesystem.c
+++ b/wsutil/filesystem.c
@@ -642,7 +642,7 @@ configuration_init_w32(const char* arg0 _U_)
             msg, error);
     }
 
-#ifdef __MINGW64__
+#ifdef HAVE_MSYSTEM
     /*
      * We already have the program_dir. Find the installation prefix.
      * This is one level up from the bin_dir. If the program_dir does
@@ -657,7 +657,7 @@ configuration_init_w32(const char* arg0 _U_)
         install_prefix = g_strdup(progfile_dir);
         running_in_build_directory_flag = TRUE;
     }
-#endif /* __MINGW64__ */
+#endif /* HAVE_MSYSTEM */
 
     return NULL;
 }
@@ -994,7 +994,7 @@ get_datafile_dir(void)
         return datafile_dir;
     }
 
-#if defined(__MINGW64__)
+#if defined(HAVE_MSYSTEM)
     if (running_in_build_directory_flag) {
         datafile_dir = g_strdup(install_prefix);
     } else {
@@ -1072,7 +1072,7 @@ get_doc_dir(void)
         ;
     }
 
-#if defined(__MINGW64__)
+#if defined(HAVE_MSYSTEM)
     if (running_in_build_directory_flag) {
         doc_dir = g_strdup(install_prefix);
     } else {
@@ -1157,7 +1157,7 @@ init_plugin_dir(void)
     }
 
 #if defined(HAVE_PLUGINS) || defined(HAVE_LUA)
-#if defined(__MINGW64__)
+#if defined(HAVE_MSYSTEM)
     if (running_in_build_directory_flag) {
         plugin_dir = g_build_filename(install_prefix, "plugins", (gchar *)NULL);
     } else {
@@ -1311,7 +1311,7 @@ init_extcap_dir(void)
         extcap_dir = g_strdup(g_getenv(extcap_dir_envar));
     }
 
-#if defined(__MINGW64__)
+#if defined(HAVE_MSYSTEM)
     else if (running_in_build_directory_flag) {
         extcap_dir = g_build_filename(install_prefix, "extcap", (gchar *)NULL);
     } else {