diff --git a/config/rules.mk b/config/rules.mk
index 701f66f8cbbe..8d418c67a526 100644
--- a/config/rules.mk
+++ b/config/rules.mk
@@ -1268,7 +1268,7 @@ ifneq ($(DIST_FILES),)
 DIST_FILES_PATH := $(FINAL_TARGET)
 # We preprocess these, but they don't necessarily have preprocessor directives,
 # so tell them preprocessor to not complain about that.
-DIST_FILES_FLAGS := $(XULAPP_DEFINES) --silence-missing-directive-warnings
+DIST_FILES_FLAGS := --silence-missing-directive-warnings
 PP_TARGETS += DIST_FILES
 endif