diff --git a/ccache.c b/ccache.c
index 88e0ec5..7dffeb4 100644
--- a/ccache.c
+++ b/ccache.c
@@ -1762,6 +1762,7 @@ calculate_object_hash(struct args *args, struct mdfour *hash, int direct_mode)
 			"CPLUS_INCLUDE_PATH",
 			"OBJC_INCLUDE_PATH",
 			"OBJCPLUS_INCLUDE_PATH", // clang
+			"GCC_HONOUR_COPTS",
 			NULL
 		};
 		for (const char **p = envvars; *p; ++p) {