diff --git a/block-migration.c b/block-migration.c
index 9ac7de6d78f3dcac154aa87cbef476f00c77c2a4..573319a305d56f124bcee7f7fcc7e824ead97ce3 100644
--- a/block-migration.c
+++ b/block-migration.c
@@ -695,7 +695,7 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
                    (addr == 100) ? '\n' : '\r');
             fflush(stdout);
         } else if (!(flags & BLK_MIG_FLAG_EOS)) {
-            fprintf(stderr, "Unknown flags\n");
+            fprintf(stderr, "Unknown block migration flags: %#x\n", flags);
             return -EINVAL;
         }
         ret = qemu_file_get_error(f);