diff --git a/src/library/type_context.h b/src/library/type_context.h
index ac18d9e30b..82f865fdb3 100644
--- a/src/library/type_context.h
+++ b/src/library/type_context.h
@@ -5,6 +5,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Author: Leonardo de Moura
 */
 #pragma once
+#include <vector>
 #include "library/metavar_context.h"
 
 namespace lean {