--- a/dom/presentation/provider/MulticastDNSDeviceProvider.cpp
+++ b/dom/presentation/provider/MulticastDNSDeviceProvider.cpp
@@ -571,28 +571,30 @@ MulticastDNSDeviceProvider::ForceDiscove
   if (!mDiscoveryEnabled) {
     return NS_OK;
   }
 
   MOZ_ASSERT(mDiscoveryTimer);
   MOZ_ASSERT(mMulticastDNS);
 
   // if it's already discovering, extend existing discovery timeout.
+  nsresult rv;
   if (mIsDiscovering) {
     Unused << mDiscoveryTimer->Cancel();
 
-    NS_WARN_IF(NS_FAILED(mDiscoveryTimer->Init(this,
-                                               mDiscveryTimeoutMs,
-                                               nsITimer::TYPE_ONE_SHOT)));
+    if (NS_WARN_IF(NS_FAILED( rv = mDiscoveryTimer->Init(this,
+        mDiscveryTimeoutMs,
+        nsITimer::TYPE_ONE_SHOT)))) {
+        return rv;
+    }
     return NS_OK;
   }
 
   StopDiscovery(NS_OK);
 
-  nsresult rv;
   if (NS_WARN_IF(NS_FAILED(rv = mMulticastDNS->StartDiscovery(
       NS_LITERAL_CSTRING(SERVICE_TYPE),
       mWrappedListener,
       getter_AddRefs(mDiscoveryRequest))))) {
     return rv;
   }
 
   return NS_OK;