diff --git a/monitor.c b/monitor.c
index dc4583f..e85f990 100644
--- a/monitor.c
+++ b/monitor.c
@@ -97,6 +97,7 @@ typedef struct MonitorControl {
     uint8_t buf[1024];
     int size;
     QObject *id;
+    int print_enabled;
 } MonitorControl;
 
 struct Monitor {
@@ -184,9 +185,13 @@ static void monitor_puts(Monitor *mon, const char *str)
 
 void monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
 {
-    char buf[4096];
-    vsnprintf(buf, sizeof(buf), fmt, ap);
-    monitor_puts(mon, buf);
+    if (mon->mc && !mon->mc->print_enabled) {
+        qemu_error_new(QERR_UNDEFINED_ERROR, "monitor print");
+    } else {
+        char buf[4096];
+        vsnprintf(buf, sizeof(buf), fmt, ap);
+        monitor_puts(mon, buf);
+    }
 }
 
 void monitor_printf(Monitor *mon, const char *fmt, ...)
@@ -270,7 +275,10 @@ static void monitor_json_emitter(Monitor *mon, const QObject *data)
     json = qobject_to_json(data);
     assert(json != NULL);
 
+    mon->mc->print_enabled = 1;
     monitor_printf(mon, "%s\n", qstring_get_str(json));
+    mon->mc->print_enabled = 0;
+
     QDECREF(json);
 }