diff --git a/libp2p/stream_muxer/mplex/exceptions.py b/libp2p/stream_muxer/mplex/exceptions.py
new file mode 100644
index 0000000..74a6ade
--- /dev/null
+++ b/libp2p/stream_muxer/mplex/exceptions.py
@@ -0,0 +1,2 @@
+class StreamNotFound(Exception):
+    pass