diff --git a/netwerk/protocol/res/nsResProtocolHandler.cpp b/netwerk/protocol/res/nsResProtocolHandler.cpp
index 8122c0d6405..4ae6916d029 100644
--- a/netwerk/protocol/res/nsResProtocolHandler.cpp
+++ b/netwerk/protocol/res/nsResProtocolHandler.cpp
@@ -411,25 +411,7 @@ nsResProtocolHandler::SetSubstitution(const nsACString& root, nsIURI *baseURI)
         return NS_OK;
     }
 
-    // If baseURI isn't a resource URI, we can set the substitution immediately.
-    nsCAutoString scheme;
-    nsresult rv = baseURI->GetScheme(scheme);
-    NS_ENSURE_SUCCESS(rv, rv);
-    if (!scheme.Equals(NS_LITERAL_CSTRING("resource"))) {
-        return mSubstitutions.Put(root, baseURI) ? NS_OK : NS_ERROR_UNEXPECTED;
-    }
-
-    // baseURI is a resource URI, let's resolve it first.
-    nsCAutoString newBase;
-    rv = ResolveURI(baseURI, newBase);
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    nsCOMPtr<nsIURI> newBaseURI;
-    rv = mIOService->NewURI(newBase, nsnull, nsnull,
-                            getter_AddRefs(newBaseURI));
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    return mSubstitutions.Put(root, newBaseURI) ? NS_OK : NS_ERROR_UNEXPECTED;
+    return mSubstitutions.Put(root, baseURI) ? NS_OK : NS_ERROR_UNEXPECTED;
 }
 
 NS_IMETHODIMP
diff --git a/netwerk/test/unit/test_bug580508.js b/netwerk/test/unit/test_bug580508.js
deleted file mode 100644
index 278d78eb294..00000000000
--- a/netwerk/test/unit/test_bug580508.js
+++ /dev/null
@@ -1,29 +0,0 @@
-const Cc = Components.classes;
-const Ci = Components.interfaces;
-
-let ioService = Cc["@mozilla.org/network/io-service;1"]
-                .getService(Ci.nsIIOService);
-let resProt = ioService.getProtocolHandler("resource")
-              .QueryInterface(Ci.nsIResProtocolHandler);
-
-function run_test() {
-    // Define a resource:// alias that points to another resource:// URI.
-    let greModulesURI = ioService.newURI("resource://gre/modules/", null, null);
-    resProt.setSubstitution("my-gre-modules", greModulesURI);
-
-    // When we ask for the alias, we should not get the resource://
-    // URI that we registered it for but the original file URI.
-    let greFileSpec = ioService.newURI("modules/", null,
-                                       resProt.getSubstitution("gre")).spec;
-    let aliasURI = resProt.getSubstitution("my-gre-modules");
-    do_check_eq(aliasURI.spec, greFileSpec);
-
-    // Resolving URIs using the original resource path and the alias
-    // should yield the same result.
-    let greNetUtilURI = ioService.newURI("resource://gre/modules/NetUtil.jsm",
-                                         null, null);
-    let myNetUtilURI = ioService.newURI("resource://my-gre-modules/NetUtil.jsm",
-                                        null, null);
-    do_check_eq(resProt.resolveURI(greNetUtilURI),
-                resProt.resolveURI(myNetUtilURI));
-}