diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index 56b5006c9dd..4ec787854d6 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -9262,12 +9262,25 @@ nsClassifierCallback::Run()
     nsresult rv = channel->GetURI(getter_AddRefs(uri));
     NS_ENSURE_SUCCESS(rv, rv);
 
-    // XXX: we need to audit other channels to make sure they can handle
-    // being suspended directly after AsyncOpen()
-    nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(channel);
-    if (!httpChannel) {
-        return NS_OK;
-    }
+    // Don't bother checking certain types of URIs.
+    PRBool hasFlags;
+    rv = NS_URIChainHasFlags(uri,
+                             nsIProtocolHandler::URI_DANGEROUS_TO_LOAD,
+                             &hasFlags);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (hasFlags) return NS_OK;
+
+    rv = NS_URIChainHasFlags(uri,
+                             nsIProtocolHandler::URI_IS_LOCAL_FILE,
+                             &hasFlags);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (hasFlags) return NS_OK;
+
+    rv = NS_URIChainHasFlags(uri,
+                             nsIProtocolHandler::URI_IS_UI_RESOURCE,
+                             &hasFlags);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (hasFlags) return NS_OK;
 
     nsCOMPtr<nsIURIClassifier> uriClassifier =
         do_GetService(NS_URICLASSIFIERSERVICE_CONTRACTID, &rv);
@@ -9281,7 +9294,13 @@ nsClassifierCallback::Run()
         // Suspend the channel, it will be resumed when we get the classifier
         // callback.
         rv = channel->Suspend();
-        NS_ENSURE_SUCCESS(rv, rv);
+        if (NS_FAILED(rv)) {
+            // Some channels (including nsJSChannel) fail on Suspend.  This
+            // shouldn't be fatal, but will prevent malware from being
+            // blocked on these channels.
+            return NS_OK;
+        }
+
         mSuspendedChannel = channel;
 #ifdef DEBUG
         PR_LOG(gDocShellLog, PR_LOG_DEBUG,