diff --git a/CMakeLists.txt b/CMakeLists.txt
index a3388dd..f0626e5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -119,12 +119,16 @@ elseif(CMAKE_COMPILER_IS_GNUCXX)
       "${CMAKE_CXX_FLAGS} -std=c++0x")
   endif(CYGWIN)
   set(CMAKE_CXX_FLAGS
-    "${CMAKE_CXX_FLAGS} -Wall -pedantic -Werror -Wextra -Werror=shadow")
+    "${CMAKE_CXX_FLAGS} -Wall -pedantic -Wextra -Werror=shadow")
   if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.4)
     if (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 7.0)
       set(CMAKE_CXX_FLAGS
         "${CMAKE_CXX_FLAGS} -faligned-new")
     endif()
+    if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 7.0)
+      set(CMAKE_CXX_FLAGS
+        "${CMAKE_CXX_FLAGS} -Wextra")
+    endif()
     set(CMAKE_CXX_FLAGS
       "${CMAKE_CXX_FLAGS} -Wunused-result -Werror=unused-result -Wunused-parameter -Werror=unused-parameter")
   endif()