diff --git a/blockdev.c b/blockdev.c
index bc7016a8d..d3500c613 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -487,7 +487,11 @@ static DriveInfo *blockdev_init(QemuOpts *all_opts,
 
         drv = bdrv_find_whitelisted_format(buf, ro);
         if (!drv) {
-            error_report("'%s' invalid format", buf);
+            if (!ro && bdrv_find_whitelisted_format(buf, !ro)) {
+                error_report("'%s' can be only used as read-only device.", buf);
+            } else {
+                error_report("'%s' invalid format", buf);
+            }
             return NULL;
         }
     }