diff --git a/m4.include/mc-cflags.m4 b/m4.include/mc-cflags.m4
index 6d250cb26..e3f7d9afc 100644
--- a/m4.include/mc-cflags.m4
+++ b/m4.include/mc-cflags.m4
@@ -73,7 +73,7 @@ dnl    MC_CHECK_ONE_CFLAG([-Wstrict-aliasing])
     MC_CHECK_ONE_CFLAG([-Wswitch])
     MC_CHECK_ONE_CFLAG([-Wtype-limits])
     MC_CHECK_ONE_CFLAG([-Wuninitialized])
-dnl    MC_CHECK_ONE_CFLAG([-Wunused-but-set-variable])
+    MC_CHECK_ONE_CFLAG([-Wunused-but-set-variable])
     MC_CHECK_ONE_CFLAG([-Wunused-function])
     MC_CHECK_ONE_CFLAG([-Wunused-label])
     MC_CHECK_ONE_CFLAG([-Wunused-parameter])