diff --git a/devtools/print_wire.c b/devtools/print_wire.c
index a87eeedc7..b3db3cb7c 100644
--- a/devtools/print_wire.c
+++ b/devtools/print_wire.c
@@ -91,7 +91,7 @@ bool printwire_s64(const char *fieldname, const u8 **cursor, size_t *plen)
 		printf("**TRUNCATED s64 %s**\n", fieldname);
 		return false;
 	}
-	printf("%ld\n", v);
+	printf("%"PRId64"\n", v);
 	return true;
 }