diff --git a/block.c b/block.c
index 39724c1..ffcf7f2 100644
--- a/block.c
+++ b/block.c
@@ -403,6 +403,9 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename,
     pstrcpy(bs->filename, sizeof(bs->filename), filename);
 
     if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv)) {
+        error_report("block-drv-whitelist prevents using format '%s'", drv->format_name);
+        /* reset errno since we're failing because of whitelist restrictions */
+        errno = EPROTONOSUPPORT;
         return -ENOTSUP;
     }