diff --git a/ArcFormats/CommonStreams.cs b/ArcFormats/CommonStreams.cs
index b2c23e07..04d6433b 100644
--- a/ArcFormats/CommonStreams.cs
+++ b/ArcFormats/CommonStreams.cs
@@ -572,7 +572,7 @@ namespace GameRes.Formats
                 {
                     write_buf[i] = (byte)(buffer[offset+i] ^ m_key);
                 }
-                BaseStream.Write (write_buf, 0, count);
+                BaseStream.Write (write_buf, 0, chunk);
                 offset += chunk;
                 count -= chunk;
             }