diff --git a/CMakeLists.txt b/CMakeLists.txt
index c37a2d18..4effb94a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -220,7 +220,7 @@ IF(MSVC)
         ENDFOREACH(flag_var)
     ENDIF()
 ELSE()
-    SET(C_FLAGS ${C_FLAGS} -Winline -Wall -Wold-style-cast)
+    SET(C_FLAGS ${C_FLAGS} -Winline -Wall $<$<COMPILE_LANGUAGE:CXX>:-Wold-style-cast>)
     CHECK_C_COMPILER_FLAG(-Wextra HAVE_W_EXTRA)
     IF(HAVE_W_EXTRA)
         SET(C_FLAGS ${C_FLAGS} -Wextra)