diff --git a/netwerk/protocol/res/nsResProtocolHandler.cpp b/netwerk/protocol/res/nsResProtocolHandler.cpp
index 48a42287b9b1..26c11ae4062f 100644
--- a/netwerk/protocol/res/nsResProtocolHandler.cpp
+++ b/netwerk/protocol/res/nsResProtocolHandler.cpp
@@ -76,6 +76,7 @@ static nsResProtocolHandler *gResHandler = nsnull;
 static PRLogModuleInfo *gResLog;
 #endif
 
+#define kAPP           NS_LITERAL_CSTRING("app")
 #define kGRE           NS_LITERAL_CSTRING("gre")
 
 //----------------------------------------------------------------------------
@@ -180,6 +181,12 @@ nsResProtocolHandler::Init()
     rv = SetSubstitution(EmptyCString(), uri);
     NS_ENSURE_SUCCESS(rv, rv);
 
+    //
+    // make resource://app/ point to the application directory or omnijar
+    //
+    rv = SetSubstitution(kAPP, uri);
+    NS_ENSURE_SUCCESS(rv, rv);
+
     //
     // make resource://gre/ point to the GRE directory
     //
diff --git a/toolkit/xre/nsXREDirProvider.cpp b/toolkit/xre/nsXREDirProvider.cpp
index f98a798d3908..2793f8bfb8da 100644
--- a/toolkit/xre/nsXREDirProvider.cpp
+++ b/toolkit/xre/nsXREDirProvider.cpp
@@ -301,9 +301,6 @@ nsXREDirProvider::GetFile(const char* aProperty, PRBool* aPersistent,
     if (NS_SUCCEEDED(rv))
       file = lf;
   }
-  else if (!strcmp(aProperty, "resource:app")) {
-    rv = GetAppDir()->Clone(getter_AddRefs(file));
-  }
 
   else if (!strcmp(aProperty, NS_APP_PROFILE_DIR_STARTUP) && mProfileDir) {
     return mProfileDir->Clone(aFile);