diff --git a/Modules/Compiler/GNU.cmake b/Modules/Compiler/GNU.cmake
index 0bb31f9e5..8d6f5dfb8 100644
--- a/Modules/Compiler/GNU.cmake
+++ b/Modules/Compiler/GNU.cmake
@@ -33,6 +33,6 @@ macro(__compiler_gnu lang)
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
   if(NOT APPLE)
-    set(CMAKE_INCLUDE_SYSTEM_FLAG_CXX "-isystem ")
+    set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
   endif(NOT APPLE)
 endmacro()