diff --git a/repos/os/include/block_session/block_session.h b/repos/os/include/block_session/block_session.h
index b137223ccb..6adbbc1af2 100644
--- a/repos/os/include/block_session/block_session.h
+++ b/repos/os/include/block_session/block_session.h
@@ -162,6 +162,11 @@ struct Block::Session : public Genode::Session
 	 */
 	virtual Tx::Source *tx() { return 0; }
 
+	/**
+	 * Return capability for packet-transmission channel
+	 */
+	virtual Genode::Capability<Tx> tx_cap() = 0;
+
 
 	/*******************
 	 ** RPC interface **
@@ -169,7 +174,7 @@ struct Block::Session : public Genode::Session
 
 	GENODE_RPC(Rpc_info, void, info, Block::sector_t *,
 	           Genode::size_t *, Operations *);
-	GENODE_RPC(Rpc_tx_cap, Genode::Capability<Tx>, _tx_cap);
+	GENODE_RPC(Rpc_tx_cap, Genode::Capability<Tx>, tx_cap);
 	GENODE_RPC(Rpc_sync, void, sync);
 	GENODE_RPC_INTERFACE(Rpc_info, Rpc_tx_cap, Rpc_sync);
 };
diff --git a/repos/os/include/block_session/client.h b/repos/os/include/block_session/client.h
index 9b5bc74d44..633ffe15a4 100644
--- a/repos/os/include/block_session/client.h
+++ b/repos/os/include/block_session/client.h
@@ -41,7 +41,7 @@ class Block::Session_client : public Genode::Rpc_client<Session>
 		               Genode::Region_map      &rm)
 		:
 			Genode::Rpc_client<Session>(session),
-			_tx(call<Rpc_tx_cap>(), rm, tx_buffer_alloc)
+			_tx(tx_cap(), rm, tx_buffer_alloc)
 		{ }
 
 
@@ -56,9 +56,13 @@ class Block::Session_client : public Genode::Rpc_client<Session>
 		}
 
 		Tx *tx_channel() { return &_tx; }
+
 		Tx::Source *tx() { return _tx.source(); }
+
 		void sync() override { call<Rpc_sync>(); }
 
+		Genode::Capability<Tx> tx_cap() override { return call<Rpc_tx_cap>(); }
+
 		/*
 		 * Wrapper for alloc_packet, allocates 2KB aligned packets
 		 */
diff --git a/repos/os/include/block_session/rpc_object.h b/repos/os/include/block_session/rpc_object.h
index 062672bde2..76b8168fc5 100644
--- a/repos/os/include/block_session/rpc_object.h
+++ b/repos/os/include/block_session/rpc_object.h
@@ -57,7 +57,7 @@ class Block::Session_rpc_object : public Genode::Rpc_object<Session, Session_rpc
 		 * This method is called by the client via an RPC call at session
 		 * construction time.
 		 */
-		Genode::Capability<Tx> _tx_cap() { return _tx.cap(); }
+		Genode::Capability<Tx> tx_cap() override { return _tx.cap(); }
 
 		Tx::Sink *tx_sink() { return _tx.sink(); }
 };