diff --git a/GameRes/Checksum.cs b/GameRes/Checksum.cs
index d6bbb257..435b3dd9 100644
--- a/GameRes/Checksum.cs
+++ b/GameRes/Checksum.cs
@@ -114,6 +114,8 @@ namespace GameRes.Utility
 
         public static uint Compute (byte[] buf, int pos, int len)
         {
+            if (0 == len)
+                return 1;
             unsafe
             {
                 fixed (byte* ptr = &buf[pos])
@@ -224,6 +226,8 @@ namespace GameRes.Utility
 
         public void Update (byte[] buf, int pos, int len)
         {
+            if (0 == len)
+                return;
             unsafe
             {
                 fixed (byte* ptr = &buf[pos])
diff --git a/GameRes/ZLibStream.cs b/GameRes/ZLibStream.cs
index 0beb7a4b..3e7ff6db 100644
--- a/GameRes/ZLibStream.cs
+++ b/GameRes/ZLibStream.cs
@@ -179,8 +179,11 @@ namespace GameRes.Compression
 
         public override void Write (byte[] buffer, int offset, int count)
         {
-            m_adler.Write (buffer, offset, count);
-            m_total_in += count;
+            if (count > 0)
+            {
+                m_adler.Write (buffer, offset, count);
+                m_total_in += count;
+            }
         }
 
         public override void WriteByte (byte value)