diff --git a/webapprt/Makefile.in b/webapprt/Makefile.in
index 1f00df3dea01..2ae54c35567b 100644
--- a/webapprt/Makefile.in
+++ b/webapprt/Makefile.in
@@ -42,6 +42,9 @@ EXTRA_JS_MODULES = \
   WebappRT.jsm \
   $(NULL)
 
+PREF_JS_EXPORTS = $(srcdir)/prefs.js \
+                  $(NULL)
+
 include $(topsrcdir)/config/rules.mk
 
 ifdef MOZ_DEBUG
@@ -51,10 +54,6 @@ endif
 libs::
 	$(PYTHON) $(MOZILLA_DIR)/config/buildlist.py $(FINAL_TARGET)/chrome.manifest "resource webapprt ./"
 
-libs:: prefs.js
-	$(NSINSTALL) -D $(FINAL_TARGET)/defaults/preferences
-	$(INSTALL) $^ $(FINAL_TARGET)/defaults/preferences
-
 GRE_MILESTONE := $(shell tail -n 1 $(topsrcdir)/config/milestone.txt 2>/dev/null || tail -1 $(topsrcdir)/config/milestone.txt)
 GRE_BUILDID := $(shell cat $(DEPTH)/config/buildid)
 DEFINES += -DGRE_MILESTONE=$(GRE_MILESTONE) \