diff --git a/src/library/blast/simple_actions.h b/src/library/blast/simple_actions.h
index b7368208c2..2fa85c5dde 100644
--- a/src/library/blast/simple_actions.h
+++ b/src/library/blast/simple_actions.h
@@ -6,6 +6,7 @@ Author: Leonardo de Moura
 */
 #pragma once
 #include "kernel/expr.h"
+#include "library/blast/hypothesis.h"
 namespace lean {
 namespace blast {
 optional<expr> assumption_action();