diff --git a/mk/check.mk b/mk/check.mk
index 28e7ebee81a..384d4c5ab22 100644
--- a/mk/check.mk
+++ b/mk/check.mk
@@ -81,8 +81,10 @@ check-servo: $(foreach lib_crate,$(SERVO_LIB_CRATES),check-servo-$(lib_crate)) s
 
 .PHONY: check-ref
 check-ref: reftest
-	@$(call E, check: reftests)
+	@$(call E, check: reftests with GPU rendering)
 	$(Q)./reftest $(S)src/test/ref/*.list
+	@$(call E, check: reftests with CPU rendering)
+	$(Q)./reftest $(S)src/test/ref/*.list -- -c
 
 .PHONY: check-content
 check-content: contenttest