diff --git a/include/maxscale/backend.hh b/include/maxscale/backend.hh
index 7bb035268..cb4bb650f 100644
--- a/include/maxscale/backend.hh
+++ b/include/maxscale/backend.hh
@@ -100,6 +100,7 @@ public:
      */
     inline bool has_session_commands() const
     {
+        ss_dassert(in_use());
         return !m_session_commands.empty();
     }
 
diff --git a/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc b/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
index d5d741ee5..91eaf40bc 100644
--- a/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
+++ b/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
@@ -64,8 +64,8 @@ static SRWBackend compare_backends(SRWBackend a, SRWBackend b, select_criteria_t
     }
 
     // Prefer servers that are not busy executing session commands
-    bool a_busy = a->has_session_commands();
-    bool b_busy = b->has_session_commands();
+    bool a_busy = a->in_use() && a->has_session_commands();
+    bool b_busy = b->in_use() && b->has_session_commands();
 
     if (a_busy && !b_busy)
     {
diff --git a/server/modules/routing/readwritesplit/rwsplitsession.cc b/server/modules/routing/readwritesplit/rwsplitsession.cc
index 7057f736a..4a2d55658 100644
--- a/server/modules/routing/readwritesplit/rwsplitsession.cc
+++ b/server/modules/routing/readwritesplit/rwsplitsession.cc
@@ -547,12 +547,14 @@ void RWSplitSession::clientReply(GWBUF *writebuf, DCB *backend_dcb)
 
     if (backend->has_session_commands())
     {
-        /** Reply to an executed session command */
+        /** Process the reply to an executed session command. This function can
+         * close the backend if it's a slave. */
         process_sescmd_response(backend, &writebuf);
     }
 
-    if (backend->has_session_commands())
+    if (backend->in_use() && backend->has_session_commands())
     {
+        // Backend is still in use and has more session commands to execute
         if (backend->execute_session_command() && backend->is_waiting_result())
         {
             m_expected_responses++;
@@ -560,12 +562,14 @@ void RWSplitSession::clientReply(GWBUF *writebuf, DCB *backend_dcb)
     }
     else if (m_expected_responses == 0 && m_query_queue)
     {
+        // All replies received, route any stored queries
         route_stored_query();
     }
 
     if (writebuf)
     {
         ss_dassert(client_dcb);
+        ss_info_dassert(backend->in_use(), "Backend should be in use when routing reply");
         /** Write reply to client DCB */
         MXS_SESSION_ROUTE_REPLY(backend_dcb->session, writebuf);
     }