diff --git a/GameRes/ImagePNG.cs b/GameRes/ImagePNG.cs
index 3bd4973a..67eaad35 100644
--- a/GameRes/ImagePNG.cs
+++ b/GameRes/ImagePNG.cs
@@ -104,7 +104,7 @@ namespace GameRes
 
         void SkipBytes (IBinaryStream file, uint num)
         {
-            if (file.AsStream.CanSeek)
+            if (file.CanSeek)
                 file.Seek (num, SeekOrigin.Current);
             else
             {