diff --git a/external/mit/xorg/lib/libGL/Makefile b/external/mit/xorg/lib/libGL/Makefile
index d9f98eb6e28e..54af561ade30 100644
--- a/external/mit/xorg/lib/libGL/Makefile
+++ b/external/mit/xorg/lib/libGL/Makefile
@@ -212,7 +212,9 @@ PKGCONFIG_SED_FLAGS= \
 
 CWARNFLAGS.clang+=	-Wno-tautological-compare -Wno-format -Wno-constant-conversion \
 			-Wno-error=incompatible-pointer-types
+.if ${HAVE_GCC:Uno} >= 7
 CWARNFLAGS.gcc+=	-Wno-error=stringop-overflow
+.endif
 
 .include <bsd.x11.mk>
 .include <bsd.lib.mk>