diff --git a/src/bin/pg_upgrade/util.c b/src/bin/pg_upgrade/util.c
index fc20472..dc000d0 100644
--- a/src/bin/pg_upgrade/util.c
+++ b/src/bin/pg_upgrade/util.c
@@ -198,7 +198,7 @@ quote_identifier(const char *s)
 		s++;
 	}
 	*r++ = '"';
-	*r++ = '\0';
+	*r = '\0';
 
 	return result;
 }