diff --git a/util/parallel_regression.hpp b/util/parallel_regression.hpp
index f60ee84..61905bc 100644
--- a/util/parallel_regression.hpp
+++ b/util/parallel_regression.hpp
@@ -126,6 +126,7 @@ class ParallelRegressionGen : public RegressionGen<NC, EnIC, TestFlush, PAddrN,
           xact_cond[i]->wait(lk, [&, i]{return xact_queue[i].empty();});
           xact_queue[i].push_back(act);
         }
+        std::unique_lock lk(*xact_mutux[core]);
         xact_queue[core].push_back(act);
       }else{
         std::unique_lock lk(*xact_mutux[core]);