diff --git a/BurnOutSharp/External/libmspack/CHM/Implementation.cs b/BurnOutSharp/External/libmspack/CHM/Implementation.cs
index 839a963b..4ac9a862 100644
--- a/BurnOutSharp/External/libmspack/CHM/Implementation.cs
+++ b/BurnOutSharp/External/libmspack/CHM/Implementation.cs
@@ -1113,7 +1113,12 @@ namespace LibMSPackSharp.CHM
         /// </summary>
         private static int SysWrite(object file, byte[] buffer, int offset, int bytes)
         {
-            if (file is DecompressorImpl self)
+            // Null output file means skip those bytes
+            if (file == null)
+            {
+                return bytes;
+            }
+            else if (file is DecompressorImpl self)
             {
                 self.State.Offset += (uint)bytes;
                 if (self.State.OutputFileHandle != null)
diff --git a/BurnOutSharp/External/libmspack/OAB/Implementation.cs b/BurnOutSharp/External/libmspack/OAB/Implementation.cs
index 7e7b7f34..828c20ee 100644
--- a/BurnOutSharp/External/libmspack/OAB/Implementation.cs
+++ b/BurnOutSharp/External/libmspack/OAB/Implementation.cs
@@ -86,7 +86,12 @@ namespace LibMSPackSharp.OAB
 
         private static int SysWrite(object baseFile, byte[] buf, int pointer, int size)
         {
-            if (baseFile is InternalFile file)
+            // Null output file means skip those bytes
+            if (baseFile == null)
+            {
+                return size;
+            }
+            else if (baseFile is InternalFile file)
             {
                 int bytes_written = file.OrigSys.Write(file.OrigFile, buf, pointer, size);
                 if (bytes_written > 0)
@@ -100,7 +105,7 @@ namespace LibMSPackSharp.OAB
             }
 
             // Unknown file to write to
-            return 0;
+            return -1;
         }
 
         #endregion
diff --git a/BurnOutSharp/External/libmspack/SystemImpl.cs b/BurnOutSharp/External/libmspack/SystemImpl.cs
index f21bf918..2d8a66d1 100644
--- a/BurnOutSharp/External/libmspack/SystemImpl.cs
+++ b/BurnOutSharp/External/libmspack/SystemImpl.cs
@@ -252,6 +252,12 @@ namespace LibMSPackSharp
 
         private static int DefaultWrite(object file, byte[] buffer, int pointer, int bytes)
         {
+            // Null output file means skip those bytes
+            if (file == null)
+            {
+                return bytes;
+            }
+
             FileStream self = file as FileStream;
             if (self != null && buffer != null && bytes >= 0)
             {