diff --git a/dist/pdisk/pdisk.c b/dist/pdisk/pdisk.c
index ce8dc02c3338..6214c635e2c9 100644
--- a/dist/pdisk/pdisk.c
+++ b/dist/pdisk/pdisk.c
@@ -167,12 +167,12 @@ main(int argc, char **argv)
     init_program_name(argv);
 
     if (sizeof(DPME) != PBLOCK_SIZE) {
-	fatal(-1, "Size of partition map entry (%d) "
+	fatal(-1, "Size of partition map entry (%lu) "
 		"is not equal to block size (%d)\n",
 		sizeof(DPME), PBLOCK_SIZE);
     }
     if (sizeof(Block0) != PBLOCK_SIZE) {
-	fatal(-1, "Size of block zero structure (%d) "
+	fatal(-1, "Size of block zero structure (%lu) "
 		"is not equal to block size (%d)\n",
 		sizeof(Block0), PBLOCK_SIZE);
     }