--- a/netwerk/dns/nsHostResolver.cpp
+++ b/netwerk/dns/nsHostResolver.cpp
@@ -1468,17 +1468,17 @@ nsHostResolver::ThreadFunc(void *arg)
     nsCString name = naming.GetNextThreadName("DNS Resolver");
 
     AUTO_PROFILER_REGISTER_THREAD(name.BeginReading());
     NS_SetCurrentThreadName(name.BeginReading());
 
 #if defined(RES_RETRY_ON_FAILURE)
     nsResState rs;
 #endif
-    nsHostResolver *resolver = (nsHostResolver *)arg;
+    RefPtr<nsHostResolver> resolver = dont_AddRef((nsHostResolver *)arg);
     nsHostRecord *rec  = nullptr;
     AddrInfo *ai = nullptr;
 
     while (rec || resolver->GetHostToLookup(&rec)) {
         LOG(("DNS lookup thread - Calling getaddrinfo for host [%s%s%s].\n",
              LOG_HOST(rec->host, rec->netInterface)));
 
         TimeStamp startTime = TimeStamp::Now();
@@ -1532,17 +1532,17 @@ nsHostResolver::ThreadFunc(void *arg)
             // leave 'rec' assigned and loop to make a renewed host resolve
             LOG(("DNS lookup thread - Re-resolving host [%s%s%s].\n",
                  LOG_HOST(rec->host, rec->netInterface)));
         } else {
             rec = nullptr;
         }
     }
     resolver->mThreadCount--;
-    NS_RELEASE(resolver);
+    resolver = nullptr;
     LOG(("DNS lookup thread - queue empty, thread finished.\n"));
 }
 
 nsresult
 nsHostResolver::Create(uint32_t maxCacheEntries,
                        uint32_t defaultCacheEntryLifetime,
                        uint32_t defaultGracePeriod,
                        nsHostResolver **result)