diff --git a/src/solver/parallel_tactical2.cpp b/src/solver/parallel_tactical2.cpp
index 8f1045c5e..921e6dcf6 100644
--- a/src/solver/parallel_tactical2.cpp
+++ b/src/solver/parallel_tactical2.cpp
@@ -482,6 +482,8 @@ class parallel_solver {
 
         void set_cancel() {
             std::scoped_lock lock(mux);
+            if (m_state != state::is_running)
+                return;
             cancel_workers_unlocked();
         }