diff --git a/src/library/blast/intros.cpp b/src/library/blast/intros.cpp
index 1935c059ee..d8793a43c5 100644
--- a/src/library/blast/intros.cpp
+++ b/src/library/blast/intros.cpp
@@ -24,6 +24,8 @@ struct intros_proof_step_cell : public proof_step_cell {
 };
 
 bool intros_action(unsigned max) {
+    if (max == 0)
+        return true;
     state &  s  = curr_state();
     expr target = whnf(s.get_target());
     if (!is_pi(target))