diff --git a/src/machine/streams.rs b/src/machine/streams.rs
index 443c0183..253bd47e 100644
--- a/src/machine/streams.rs
+++ b/src/machine/streams.rs
@@ -836,7 +836,7 @@ impl Read for Stream {
                 ErrorKind::PermissionDenied,
                 StreamError::ReadFromOutputStream,
             )),
-            Stream::Null(_) => Ok(buf.len()),
+            Stream::Null(_) => Ok(0),
             Stream::OutputFile(_) | Stream::StandardError(_) | Stream::StandardOutput(_) => {
                 Err(std::io::Error::new(
                     ErrorKind::PermissionDenied,