diff --git a/config/rules.mk b/config/rules.mk
index e1c9dc1e455f..9987a3871040 100644
--- a/config/rules.mk
+++ b/config/rules.mk
@@ -968,7 +968,7 @@ endif # MOZ_RUST
 
 $(SOBJS):
 	$(REPORT_BUILD)
-	$(AS) -o $@ $(ASFLAGS) $($(notdir $<)_FLAGS) $(LOCAL_INCLUDES) -c $<
+	$(AS) -o $@ $(DEFINES) $(ASFLAGS) $($(notdir $<)_FLAGS) $(LOCAL_INCLUDES) -c $<
 
 $(CPPOBJS):
 	$(REPORT_BUILD_VERBOSE)