diff --git a/mozilla/config/rules.mk b/mozilla/config/rules.mk
index d751c4733e0..d47fd642f2a 100644
--- a/mozilla/config/rules.mk
+++ b/mozilla/config/rules.mk
@@ -933,7 +933,7 @@ $(XPIDL_GEN_DIR):
 $(XPIDL_GEN_DIR)/%.h: %.idl $(IDL_COMPILE) $(XPIDL_GEN_DIR)
 	$(XPIDL_COMPILE) -m header -w -I $(XPDIST)/idl -I$(srcdir) -o $(XPIDL_GEN_DIR)/$* $<
 	@if test -n "$(findstring $*.h, $(EXPORTS))"; \
-	  then echo "*** WARNING: file $*.h generated from $*.idl overrides $(srcdir)/$*.h"; fi
+	  then echo "*** WARNING: file $*.h generated from $*.idl overrides $(srcdir)/$*.h"; else true; fi
 
 export:: $(patsubst %.idl,$(XPIDL_GEN_DIR)/%.h, $(XPIDLSRCS)) $(XPDIST)/include
 	$(INSTALL) -m 444 $^