--- a/src/ccache.c
+++ b/src/ccache.c
@@ -1940,6 +1940,7 @@ calculate_object_hash(struct args *args,
 			"CPLUS_INCLUDE_PATH",
 			"OBJC_INCLUDE_PATH",
 			"OBJCPLUS_INCLUDE_PATH", // clang
+			"GCC_HONOUR_COPTS",
 			NULL
 		};
 		for (const char **p = envvars; *p; ++p) {