diff --git a/CMakeLists.txt b/CMakeLists.txt
index daf69a07f..a9f3783c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -63,7 +63,7 @@ endfunction(pexamples)
 if (ICB)
     enable_language(C CXX) # For testing binding with c/c++.
 
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
+    set(CMAKE_CXX_STANDARD 11) # OK, since cmake-3.1 only.
 
     file(WRITE ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/PROG_ICB.f90
          "