diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,7 +51,7 @@
   SET(CXX_WARNING $ENV{LEMON_CXX_WARNING})
 ELSE()
   IF(CMAKE_COMPILER_IS_GNUCXX)
-    SET(CXX_WARNING "-Wall -W -Wunused -Wformat=2 -Wctor-dtor-privacy -Wnon-virtual-dtor -Wno-char-subscripts -Wwrite-strings -Wno-char-subscripts -Wreturn-type -Wcast-qual -Wcast-align -Wsign-promo -Woverloaded-virtual -ansi -fno-strict-aliasing -Wold-style-cast -Wno-unknown-pragmas")
+    SET(CXX_WARNING "-Wall -W -Wunused -Wformat=2 -Wctor-dtor-privacy -Wnon-virtual-dtor -Wno-char-subscripts -Wwrite-strings -Wno-char-subscripts -Wreturn-type -Wcast-qual -Wcast-align -Wsign-promo -Woverloaded-virtual -fno-strict-aliasing -Wold-style-cast -Wno-unknown-pragmas")
     SET(CMAKE_CXX_FLAGS_DEBUG CACHE STRING "-ggdb")
     SET(CMAKE_C_FLAGS_DEBUG CACHE STRING "-ggdb")
   ELSEIF(MSVC)