diff --git a/Makefile b/Makefile
index 0d7647f796..50b4b3afb9 100644
--- a/Makefile
+++ b/Makefile
@@ -225,8 +225,9 @@ dtc/%:
 $(SUBDIR_RULES): libqemuutil.a libqemustub.a $(common-obj-y) $(qom-obj-y) $(crypto-aes-obj-$(CONFIG_USER_ONLY))
 
 ROMSUBDIR_RULES=$(patsubst %,romsubdir-%, $(ROMS))
+# Only keep -O and -g cflags
 romsubdir-%:
-	$(call quiet-command,$(MAKE) $(SUBDIR_MAKEFLAGS) -C pc-bios/$* V="$(V)" TARGET_DIR="$*/",)
+	$(call quiet-command,$(MAKE) $(SUBDIR_MAKEFLAGS) -C pc-bios/$* V="$(V)" TARGET_DIR="$*/" CFLAGS="$(filter -O% -g%,$(CFLAGS))",)
 
 ALL_SUBDIRS=$(TARGET_DIRS) $(patsubst %,pc-bios/%, $(ROMS))
 
diff --git a/pc-bios/optionrom/Makefile b/pc-bios/optionrom/Makefile
index 24e175e0eb..6bab490073 100644
--- a/pc-bios/optionrom/Makefile
+++ b/pc-bios/optionrom/Makefile
@@ -24,8 +24,6 @@ QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -no-integrated-as)
 QEMU_CFLAGS += -m32 -include $(SRC_PATH)/pc-bios/optionrom/code16gcc.h
 endif
 
-# Drop gcov and glib flags
-CFLAGS := $(filter -O% -g%, $(CFLAGS))
 QEMU_INCLUDES += -I$(SRC_PATH)
 
 Wa = -Wa,