diff --git a/lib/luks2/luks2_json_format.c b/lib/luks2/luks2_json_format.c
index bba29a35..5fb992be 100644
--- a/lib/luks2/luks2_json_format.c
+++ b/lib/luks2/luks2_json_format.c
@@ -247,7 +247,8 @@ int LUKS2_generate_hdr(
 		/* Decrease keyslots_size due to metadata device being too small */
 		if (!device_size(crypt_metadata_device(cd), &mdev_size) &&
 		    ((keyslots_size + get_min_offset(hdr)) > mdev_size) &&
-		    device_fallocate(crypt_metadata_device(cd), keyslots_size + get_min_offset(hdr)))
+		    device_fallocate(crypt_metadata_device(cd), keyslots_size + get_min_offset(hdr)) &&
+		    (get_min_offset(hdr) <= mdev_size))
 			keyslots_size = mdev_size - get_min_offset(hdr);
 	}