diff --git a/DepotDownloader/CDNClientPool.cs b/DepotDownloader/CDNClientPool.cs
index 4b03c89b..be45e167 100644
--- a/DepotDownloader/CDNClientPool.cs
+++ b/DepotDownloader/CDNClientPool.cs
@@ -134,10 +134,10 @@ namespace DepotDownloader
                     {
                         steamSession.RequestCDNAuthToken(appId, depotId, server.Host);
 
-                        var cdnTuple = Tuple.Create(depotId, server.Host);
+                        var cdnKey = string.Format("{0:D}:{1}", depotId, server.Host);
                         SteamApps.CDNAuthTokenCallback authTokenCallback;
 
-                        if (steamSession.CDNAuthTokens.TryGetValue(cdnTuple, out authTokenCallback))
+                        if (steamSession.CDNAuthTokens.TryGetValue(cdnKey, out authTokenCallback))
                         {
                             cdnAuthToken = authTokenCallback.Token;
                         }
@@ -180,10 +180,10 @@ namespace DepotDownloader
                 {
                     steamSession.RequestCDNAuthToken(appId, depotId, server.Host);
 
-                    var cdnTuple = Tuple.Create(depotId, server.Host);
+                    var cdnKey = string.Format("{0:D}:{1}", depotId, server.Host);
                     SteamApps.CDNAuthTokenCallback authTokenCallback;
 
-                    if (steamSession.CDNAuthTokens.TryGetValue(cdnTuple, out authTokenCallback))
+                    if (steamSession.CDNAuthTokens.TryGetValue(cdnKey, out authTokenCallback))
                     {
                         cdnAuthToken = authTokenCallback.Token;
                     }
diff --git a/DepotDownloader/Steam3Session.cs b/DepotDownloader/Steam3Session.cs
index 832e959c..fc10ad4c 100644
--- a/DepotDownloader/Steam3Session.cs
+++ b/DepotDownloader/Steam3Session.cs
@@ -1,5 +1,6 @@
 using SteamKit2;
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.IO;
@@ -30,7 +31,7 @@ namespace DepotDownloader
         public Dictionary<uint, byte[]> AppTickets { get; private set; }
         public Dictionary<uint, ulong> AppTokens { get; private set; }
         public Dictionary<uint, byte[]> DepotKeys { get; private set; }
-        public Dictionary<Tuple<uint, string>, SteamApps.CDNAuthTokenCallback> CDNAuthTokens { get; private set; }
+        public ConcurrentDictionary<string, SteamApps.CDNAuthTokenCallback> CDNAuthTokens { get; private set; }
         public Dictionary<uint, SteamApps.PICSProductInfoCallback.PICSProductInfo> AppInfo { get; private set; }
         public Dictionary<uint, SteamApps.PICSProductInfoCallback.PICSProductInfo> PackageInfo { get; private set; }
         public Dictionary<string, byte[]> AppBetaPasswords { get; private set; }
@@ -71,7 +72,7 @@ namespace DepotDownloader
             this.AppTickets = new Dictionary<uint, byte[]>();
             this.AppTokens = new Dictionary<uint, ulong>();
             this.DepotKeys = new Dictionary<uint, byte[]>();
-            this.CDNAuthTokens = new Dictionary<Tuple<uint, string>, SteamApps.CDNAuthTokenCallback>();
+            this.CDNAuthTokens = new ConcurrentDictionary<string, SteamApps.CDNAuthTokenCallback>();
             this.AppInfo = new Dictionary<uint, SteamApps.PICSProductInfoCallback.PICSProductInfo>();
             this.PackageInfo = new Dictionary<uint, SteamApps.PICSProductInfoCallback.PICSProductInfo>();
             this.AppBetaPasswords = new Dictionary<string, byte[]>();
@@ -287,7 +288,9 @@ namespace DepotDownloader
 
         public void RequestCDNAuthToken(uint appid, uint depotid, string host)
         {
-            if (CDNAuthTokens.ContainsKey(Tuple.Create(depotid, host)) || bAborted)
+            var cdnKey = string.Format("{0:D}:{1}", depotid, host); 
+
+            if (CDNAuthTokens.ContainsKey(cdnKey) || bAborted)
                 return;
 
             bool completed = false;
@@ -302,7 +305,7 @@ namespace DepotDownloader
                     return;
                 }
 
-                CDNAuthTokens[Tuple.Create(depotid, host)] = cdnAuth;
+                CDNAuthTokens.TryAdd(cdnKey, cdnAuth);
             };
 
             WaitUntilCallback(() =>