diff --git a/server/core/dcb.c b/server/core/dcb.c
index 0180ea08d..e6a7abd82 100644
--- a/server/core/dcb.c
+++ b/server/core/dcb.c
@@ -388,25 +388,19 @@ DCB_CALLBACK		*cb;
                  */
                 {
                         SESSION *local_session = dcb->session;
+			dcb->session = NULL;
                         CHK_SESSION(local_session);
-                        /*<
-                         * Remove reference from session if dcb is client.
-                         */
-                        if (local_session->client == dcb) {
-                            local_session->client = NULL;
-                        }
                         /** 
 			 * Set session's client pointer NULL so that other threads
 			 * won't try to call dcb_close for client DCB
 			 * after this call.
 			 */
-                        if (dcb->session->client == dcb)
+                        if (local_session->client == dcb)
 			{
-				spinlock_acquire(&dcb->session->ses_lock);
-				dcb->session->client = NULL;
-				spinlock_release(&dcb->session->ses_lock);
+				spinlock_acquire(&local_session->ses_lock);
+				local_session->client = NULL;
+				spinlock_release(&local_session->ses_lock);
 			}
-	                dcb->session = NULL;                        
 			session_free(local_session);
 		}
 	}
diff --git a/server/modules/protocol/mysql_backend.c b/server/modules/protocol/mysql_backend.c
index f74a2eebe..639379f56 100644
--- a/server/modules/protocol/mysql_backend.c
+++ b/server/modules/protocol/mysql_backend.c
@@ -1153,7 +1153,12 @@ gw_backend_close(DCB *dcb)
         mysql_send_com_quit(dcb, 0, quitbuf);
         
         mysql_protocol_done(dcb);
-
+	/** 
+	 * The lock is needed only to protect the read of session->state and 
+	 * session->client values. Client's state may change by other thread
+	 * but client's close and adding client's DCB to zombies list is executed
+	 * only if client's DCB's state does _not_ change in parallel.
+	 */
 	spinlock_acquire(&session->ses_lock);
 	/** 
 	 * If session->state is STOPPING, start closing client session. 
@@ -1162,15 +1167,13 @@ gw_backend_close(DCB *dcb)
         if (session != NULL && 
 		session->state == SESSION_STATE_STOPPING &&
 		session->client != NULL)
-        {
-                client_dcb = session->client;
-		
-                if (client_dcb->state == DCB_STATE_POLLING)
+        {		
+                if (session->client->state == DCB_STATE_POLLING)
                 {
 			spinlock_release(&session->ses_lock);
 			
                         /** Close client DCB */
-                        dcb_close(client_dcb);
+                        dcb_close(session->client);
                 }
                 else 
 		{