diff --git a/core/src/muxing.rs b/core/src/muxing.rs
index 06534e7a8346..847a193b8322 100644
--- a/core/src/muxing.rs
+++ b/core/src/muxing.rs
@@ -138,7 +138,7 @@ impl<T> StreamMuxerEvent<T> {
 
     /// Map the stream within [`StreamMuxerEvent::InboundSubstream`] and
     /// [`StreamMuxerEvent::OutboundSubstream`] to a new type.
-    pub fn map_stream<O>(self, map: impl FnOnce(O) -> O) -> StreamMuxerEvent<O> {
+    pub fn map_stream<O>(self, map: impl FnOnce(T) -> O) -> StreamMuxerEvent<O> {
         match self {
             StreamMuxerEvent::InboundSubstream(stream) => {
                 StreamMuxerEvent::InboundSubstream(map(stream))