Fixed missing compatibile format string.

Change-Id: I14244dc5e0a03b417119b398cc4672c826922e24
diff --git a/citadel/updater/updater.cpp b/citadel/updater/updater.cpp
index 111674b..776401e 100644
--- a/citadel/updater/updater.cpp
+++ b/citadel/updater/updater.cpp
@@ -380,7 +380,7 @@
 
   if (is_app_success(retval)) {
     if (buffer.size() < sizeof(stats)) {
-      fprintf(stderr, "Only got %lud / %lud bytes back",
+      fprintf(stderr, "Only got %zd / %zd bytes back",
               buffer.size(), sizeof(stats));
       return -1;
     }