Index: openmp/runtime/src/kmp_os.h
===================================================================
--- openmp/runtime/src/kmp_os.h
+++ openmp/runtime/src/kmp_os.h
@@ -300,12 +300,16 @@
 // case label is intentional and should not be diagnosed by a compiler
 //   Code from libcxx/include/__config
 // Use a function like macro to imply that it must be followed by a semicolon
-#if __cplusplus > 201402L && __has_cpp_attribute(fallthrough)
-#  define KMP_FALLTHROUGH() [[fallthrough]]
-#elif __has_cpp_attribute(clang::fallthrough)
-#  define KMP_FALLTHROUGH() [[clang::fallthrough]]
-#elif __has_attribute(fallthough) || _GNUC_VER >= 700
-#  define KMP_FALLTHROUGH() __attribute__((__fallthrough__))
+#if __GNUC__ >= 5
+#  if __cplusplus > 201402L && __has_cpp_attribute(fallthrough)
+#    define KMP_FALLTHROUGH() [[fallthrough]]
+#  elif __has_cpp_attribute(clang::fallthrough)
+#    define KMP_FALLTHROUGH() [[clang::fallthrough]]
+#  elif __has_attribute(fallthough) || __GNUC__ >= 7
+#    define KMP_FALLTHROUGH() __attribute__((__fallthrough__))
+#  else
+#    define KMP_FALLTHROUGH() ((void)0)
+#  endif
 #else
 #  define KMP_FALLTHROUGH() ((void)0)
 #endif