diff --git a/monitor.c b/monitor.c
index 99b6ed9060..6db2ba4d7a 100644
--- a/monitor.c
+++ b/monitor.c
@@ -189,6 +189,7 @@ struct Monitor {
     int suspend_cnt;
     bool skip_flush;
     QString *outbuf;
+    guint watch;
     ReadLineState *rs;
     MonitorControl *mc;
     CPUState *mon_cpu;
@@ -263,7 +264,10 @@ int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
 static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond,
                                   void *opaque)
 {
-    monitor_flush(opaque);
+    Monitor *mon = opaque;
+
+    mon->watch = 0;
+    monitor_flush(mon);
     return FALSE;
 }
 
@@ -294,7 +298,10 @@ void monitor_flush(Monitor *mon)
             QDECREF(mon->outbuf);
             mon->outbuf = tmp;
         }
-        qemu_chr_fe_add_watch(mon->chr, G_IO_OUT, monitor_unblocked, mon);
+        if (mon->watch == 0) {
+            mon->watch = qemu_chr_fe_add_watch(mon->chr, G_IO_OUT,
+                                               monitor_unblocked, mon);
+        }
     }
 }