diff --git a/Makefile b/Makefile
index 6d7a01598..f28ed5809 100644
--- a/Makefile
+++ b/Makefile
@@ -186,6 +186,7 @@ SPEC_CFLAGS += $(call cc-nowarn,clobbered)
 SPEC_CFLAGS += $(call cc-nowarn,missing-field-initializers)
 SPEC_CFLAGS += $(call cc-nowarn,implicit-fallthrough)
 SPEC_CFLAGS += $(call cc-nowarn,stringop-overflow)
+SPEC_CFLAGS += $(call cc-nowarn,cast-function-type)
 SPEC_CFLAGS += $(call cc-opt,-Wtype-limits)
 SPEC_CFLAGS += $(call cc-opt,-Wshift-negative-value)
 SPEC_CFLAGS += $(call cc-opt,-Wshift-overflow=2)