Fix memory leak
diff --git a/src/core/lib/surface/completion_queue.c b/src/core/lib/surface/completion_queue.c
index 8067b10..14e55ed 100644
--- a/src/core/lib/surface/completion_queue.c
+++ b/src/core/lib/surface/completion_queue.c
@@ -946,6 +946,7 @@
   gpr_mu_lock(cq->mu);
   if (cqd->shutdown_called) {
     gpr_mu_unlock(cq->mu);
+    GRPC_CQ_INTERNAL_UNREF(exec_ctx, cq, "shutting_down");
     GPR_TIMER_END("grpc_completion_queue_shutdown", 0);
     return;
   }