diff --git a/toolkit/mozapps/extensions/test/Makefile.in b/toolkit/mozapps/extensions/test/Makefile.in
index b29d196c046f..03014ed77976 100644
--- a/toolkit/mozapps/extensions/test/Makefile.in
+++ b/toolkit/mozapps/extensions/test/Makefile.in
@@ -63,9 +63,8 @@ _CHROME_FILES = \
 
 include $(topsrcdir)/config/rules.mk
 
-# disabled due to potentially breaking other tests
-# libs:: $(_CHROME_FILES)
-# 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/chrome/$(relativesrcdir)
+libs:: $(_CHROME_FILES)
+	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/chrome/$(relativesrcdir)
 
 libs::
 	rm -rf $(TESTXPI)