diff -up comm-beta/mozilla/Makefile.in.system-nspr comm-beta/mozilla/Makefile.in
--- comm-beta/mozilla/Makefile.in.system-nspr	2013-06-25 10:01:31.000000000 +0200
+++ comm-beta/mozilla/Makefile.in	2013-07-22 13:21:38.652481798 +0200
@@ -67,7 +67,9 @@ config.status: $(topsrcdir)/configure
 export::
 	$(RM) -r $(DIST)/sdk
 	$(MAKE) -C config export
+ifndef MOZ_NATIVE_NSPR
 	$(MAKE) tier_nspr
+endif
 
 ifdef ENABLE_TESTS
 # Additional makefile targets to call automated test suites