diff --git a/src/lua/CMakeLists.txt b/src/lua/CMakeLists.txt
index 56c70d280..f2f8b9768 100644
--- a/src/lua/CMakeLists.txt
+++ b/src/lua/CMakeLists.txt
@@ -89,6 +89,11 @@ if(LUA_ANSI)
 	set(COMMON_CFLAGS "${COMMON_CFLAGS} -DLUA_ANSI")
 endif(LUA_ANSI)
 
+#
+# COMMON_CFLAGS has no effect without this line
+#
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${COMMON_CFLAGS}")
+
 #
 # standard flags to use for each build type.
 #