diff --git a/DepotDownloader/ContentDownloader.cs b/DepotDownloader/ContentDownloader.cs
index 726df929..cc41cf98 100644
--- a/DepotDownloader/ContentDownloader.cs
+++ b/DepotDownloader/ContentDownloader.cs
@@ -1059,18 +1059,7 @@ namespace DepotDownloader
                             {
                                 fsOld.Seek((long)match.OldChunk.Offset, SeekOrigin.Begin);
 
-                                uint a = 0, b = 0;
-
-                                for (var i = 0; i < match.OldChunk.UncompressedLength; i++)
-                                {
-                                    var c = (uint)fsOld.ReadByte();
-
-                                    // adler hash
-                                    a = (a + c) % 65521;
-                                    b = (b + a) % 65521;
-                                }
-
-                                var adler = BitConverter.GetBytes(a | (b << 16));
+                                var adler = Util.AdlerHash(fsOld, (int)match.OldChunk.UncompressedLength);
                                 if (!adler.SequenceEqual(match.OldChunk.Checksum))
                                 {
                                     neededChunks.Add(match.NewChunk);
diff --git a/DepotDownloader/Util.cs b/DepotDownloader/Util.cs
index 5157d92e..e53c2726 100644
--- a/DepotDownloader/Util.cs
+++ b/DepotDownloader/Util.cs
@@ -83,18 +83,7 @@ namespace DepotDownloader
             {
                 fs.Seek((long)data.Offset, SeekOrigin.Begin);
 
-                uint a = 0, b = 0;
-
-                for (var i = 0; i < data.UncompressedLength; i++)
-                {
-                    var c = (uint)fs.ReadByte();
-
-                    // adler hash
-                    a = (a + c) % 65521;
-                    b = (b + a) % 65521;
-                }
-
-                var adler = BitConverter.GetBytes(a | (b << 16));
+                var adler = AdlerHash(fs, (int)data.UncompressedLength);
                 if (!adler.SequenceEqual(data.Checksum))
                 {
                     neededChunks.Add(data);
@@ -104,6 +93,20 @@ namespace DepotDownloader
             return neededChunks;
         }
 
+        public static byte[] AdlerHash(Stream stream, int length)
+        {
+            uint a = 0, b = 0;
+            for (var i = 0; i < length; i++)
+            {
+                var c = (uint)stream.ReadByte();
+
+                a = (a + c) % 65521;
+                b = (b + a) % 65521;
+            }
+
+            return BitConverter.GetBytes(a | (b << 16));
+        }
+
         public static byte[] DecodeHexString(string hex)
         {
             if (hex == null)