diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
index a45b61e7eddf68ee9f3b7f1c1b93482d5d58f1ef..1088a26f8e7212ea8b4c641228005758cc26af8e 100644
--- a/hw/qdev-properties.c
+++ b/hw/qdev-properties.c
@@ -351,8 +351,13 @@ static int parse_chr(DeviceState *dev, Property *prop, const char *str)
     CharDriverState **ptr = qdev_get_prop_ptr(dev, prop);
 
     *ptr = qemu_chr_find(str);
-    if (*ptr == NULL)
+    if (*ptr == NULL) {
         return -ENOENT;
+    }
+    if ((*ptr)->assigned) {
+        return -EEXIST;
+    }
+    (*ptr)->assigned = 1;
     return 0;
 }
 
diff --git a/qemu-char.c b/qemu-char.c
index cad35d7717dfb75680ccee1d80ca61e21807a614..c4557c30d06adc9dc09750481d376ee8a403f80f 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -197,6 +197,10 @@ void qemu_chr_add_handlers(CharDriverState *s,
                            IOEventHandler *fd_event,
                            void *opaque)
 {
+    if (!opaque) {
+        /* chr driver being released. */
+        s->assigned = 0;
+    }
     s->chr_can_read = fd_can_read;
     s->chr_read = fd_read;
     s->chr_event = fd_event;
diff --git a/qemu-char.h b/qemu-char.h
index 56d9954c527a712daf16615bac315fbaa06e2f6c..fb96eef3de73f0cbc7c29d473c2ca2296147b308 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -70,6 +70,7 @@ struct CharDriverState {
     char *label;
     char *filename;
     int opened;
+    int assigned; /* chardev assigned to a device */
     QTAILQ_ENTRY(CharDriverState) next;
 };