diff --git a/toolkit/mozapps/extensions/test/Makefile.in b/toolkit/mozapps/extensions/test/Makefile.in
index 03014ed7797..b29d196c046 100644
--- a/toolkit/mozapps/extensions/test/Makefile.in
+++ b/toolkit/mozapps/extensions/test/Makefile.in
@@ -63,8 +63,9 @@ _CHROME_FILES = \
 
 include $(topsrcdir)/config/rules.mk
 
-libs:: $(_CHROME_FILES)
-	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/chrome/$(relativesrcdir)
+# disabled due to potentially breaking other tests
+# libs:: $(_CHROME_FILES)
+# 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/chrome/$(relativesrcdir)
 
 libs::
 	rm -rf $(TESTXPI)