diff --git a/verify.c b/verify.c
index f537553..ea1a911 100644
--- a/verify.c
+++ b/verify.c
@@ -501,7 +501,7 @@
 	log_err("trim: verify failed at file %s offset %llu, length %lu"
 		", block offset %lu\n",
 			io_u->file->file_name, io_u->offset, io_u->buflen,
-			(p - io_u->buf));
+			(unsigned long) (p - io_u->buf));
 	return ret;
 }