diff --git a/BeefLibs/corlib/src/IO/Substream.bf b/BeefLibs/corlib/src/IO/Substream.bf
index dbc0dca7..a7a83288 100644
--- a/BeefLibs/corlib/src/IO/Substream.bf
+++ b/BeefLibs/corlib/src/IO/Substream.bf
@@ -8,16 +8,18 @@ namespace System.IO
 		Stream mChildStream ~ { if (mOwnsStream) delete _; };
 		int64 mOffset;
 		int64 mLength;
+		int64 mPosition;
 
 		public override int64 Position
 		{
 			get
 			{
-				return mChildStream.Position + mOffset;
+				return mPosition;
 			}
 
 			set
 			{
+				mPosition = value;
 				mChildStream.Position = value + mOffset;
 			}
 		}
@@ -50,6 +52,7 @@ namespace System.IO
 		public this(Stream childStream, int64 offset, int64 length, bool ownsStream = false)
 		{
 			mChildStream = childStream;
+			mChildStream.Position = offset;
 			mOffset = offset;
 			mLength = length;
 			mOwnsStream = ownsStream;
@@ -57,12 +60,38 @@ namespace System.IO
 
 		public override Result<int> TryRead(Span<uint8> data)
 		{
-			return mChildStream.TryRead(data);
+			var tryData = data;
+			if (mPosition + data.Length > mLength)
+			{
+				tryData.Length = mLength - mPosition;
+			}
+
+			switch (mChildStream.TryRead(tryData))
+			{
+			case .Ok(let len):
+				mPosition += len;
+				return .Ok(len);
+			case .Err(let err):
+				return .Err(err);
+			}
 		}
 
 		public override Result<int> TryWrite(Span<uint8> data)
 		{
-			return mChildStream.TryWrite(data);
+			var tryData = data;
+			if (mPosition + data.Length > mLength)
+			{
+				tryData.Length = mLength - mPosition;
+			}
+
+			switch (mChildStream.TryWrite(tryData))
+			{
+			case .Ok(let len):
+				mPosition += len;
+				return .Ok(len);
+			case .Err(let err):
+				return .Err(err);
+			}
 		}
 
 		public override void Close()