diff --git a/stream.prs b/stream.prs
index 918c8f9..a565087 100644
--- a/stream.prs
+++ b/stream.prs
@@ -1,7 +1,10 @@
 version 1 .
 embeddedType EntityRef.Ref .
 
+; Assertions
 StreamConnection = <stream-connection @source #!Source @sink #!Sink @spec any>.
+StreamSpecListenable = <stream-spec-listenable @spec any>.
+StreamSpecConnectable = <stream-spec-connectable @spec any>.
 
 ; Assertion
 StreamListener = <stream-listener @spec any @handle #!ConnectionHandler>.
diff --git a/tcp.prs b/tcp.prs
index 7a6d5e1..b00df01 100644
--- a/tcp.prs
+++ b/tcp.prs
@@ -5,3 +5,5 @@ TcpRemote = <tcp-remote @host string @port int>.
 TcpLocal = <tcp-local @host string @port int>.
 
 TcpPeerInfo = <tcp-peer @handle #!any @local TcpLocal @remote TcpRemote>.
+
+TcpListenError = <tcp-listen-error @spec TcpLocal @message string>.