--- a/Modules/CMakePlatformId.h.in
+++ b/Modules/CMakePlatformId.h.in
@@ -77,6 +77,9 @@
 #elif defined(__XENIX__) || defined(_XENIX) || defined(XENIX)
 # define PLATFORM_ID "Xenix"
 
+#elif defined(__GNU__)
+# define PLATFORM_ID "GNU"
+
 #else /* unknown platform */
 # define PLATFORM_ID ""
 
--- a/Modules/CMakeFortranCompilerId.F.in
+++ b/Modules/CMakeFortranCompilerId.F.in
@@ -98,6 +98,8 @@
         PRINT *, 'INFO:platform[ULTRIX]'
 #elif defined(__XENIX__) || defined(_XENIX) || defined(XENIX)
         PRINT *, 'INFO:platform[Xenix]'
+#elif defined(__GNU__)
+        PRINT *, 'INFO:platform[GNU]'
 #elif 1
 #       if 0
 !       The above 'elif 1' instead of 'else' is to work around a bug in the