diff --git a/dtc.c b/dtc.c
index 9c30c33..bb1e52b 100644
--- a/dtc.c
+++ b/dtc.c
@@ -216,7 +216,7 @@ int main(int argc, char *argv[])
 			alignsize = strtol(optarg, NULL, 0);
 			if (!is_power_of_2(alignsize))
 				die("Invalid argument \"%d\" to -a option\n",
-				    optarg);
+				    alignsize);
 			break;
 		case 'f':
 			force = true;
diff --git a/util.h b/util.h
index f5c4f1b..35b2bda 100644
--- a/util.h
+++ b/util.h
@@ -53,7 +53,7 @@ static inline void *xrealloc(void *p, size_t len)
 	void *new = realloc(p, len);
 
 	if (!new)
-		die("realloc() failed (len=%d)\n", len);
+		die("realloc() failed (len=%zd)\n", len);
 
 	return new;
 }