diff --git a/cache/coherence_multi.hpp b/cache/coherence_multi.hpp
index 28973d5..786d36e 100644
--- a/cache/coherence_multi.hpp
+++ b/cache/coherence_multi.hpp
@@ -160,6 +160,7 @@ class OuterCohPortMultiThreadT : public OPUC
     bool hit = cache->hit(addr, &ai, &s, &w, Priority::probe);
     if(hit){
       std::tie(meta, data) = cache->access_line(ai, s, w);
+      cache->lock_line(ai, s, w);
       /** It is possible that higher priority behaviors have caused the meta to change, so need check again */
       if(!meta->is_valid() || meta->addr(s) != addr){
         cache->unlock_line(ai, s, w);
diff --git a/cache/metadata.hpp b/cache/metadata.hpp
index bcad6d7..4d075e7 100644
--- a/cache/metadata.hpp
+++ b/cache/metadata.hpp
@@ -5,10 +5,9 @@
 #include <string>
 #include "util/concept_macro.hpp"
 #include <mutex>
-
-#ifndef NDEBUG
+#include <atomic>
+#include <thread>
 #include <cassert>
-#endif
 
 class CMDataBase
 {
@@ -220,11 +219,35 @@ using MetadataDirectory = MetadataMixer<AW, IW, TOfst, MT>;
 template <typename MT> requires C_DERIVE<MT, CMMetadataCommon>
 class MetaLock : public MT {
   std::mutex mtx;
+
+#ifndef NDEBUG
+  // verify no double lock or unlock
+  std::hash<std::thread::id> hasher;
+  std::atomic<uint64_t> locked;
+#endif
+
 public:
   MetaLock() : MT() {}
   virtual ~MetaLock() {}
-  virtual void lock() { mtx.lock(); }
-  virtual void unlock() { mtx.unlock(); }
+  virtual void lock() {
+#ifndef NDEBUG
+    uint64_t thread_id = hasher(std::this_thread::get_id());
+    assert(locked.load() != thread_id || 0 ==
+            "This cache line has already be locked by this thread and should not be locked by this thread again!");
+#endif
+    mtx.lock();
+#ifndef NDEBUG
+    locked = thread_id;
+#endif
+  }
+  virtual void unlock() {
+#ifndef NDEBUG
+    assert(locked.load() != 0 || 0 ==
+           "This cache line has already be unlocked and should not be unlocked again!");
+    locked = 0;
+#endif
+    mtx.unlock();
+  }
 };
 
 #endif
diff --git a/util/monitor.hpp b/util/monitor.hpp
index c278fc9..a99e595 100644
--- a/util/monitor.hpp
+++ b/util/monitor.hpp
@@ -240,8 +240,8 @@ class SimpleTracerMT : public SimpleTracer
 {
   PrintPool pool;
   std::thread print_thread;
+  std::hash<std::thread::id> hasher;
   virtual void print(std::string& msg) {
-    std::hash<std::thread::id> hasher;
     uint16_t id = hasher(std::this_thread::get_id());
     std::string msg_ext = (boost::format("thread %04x: %s") % id % msg).str();
     pool.add(msg_ext);
diff --git a/util/multithread.hpp b/util/multithread.hpp
index 1df8f81..07fa7cb 100644
--- a/util/multithread.hpp
+++ b/util/multithread.hpp
@@ -108,5 +108,4 @@ class PendingXact<false> {
 };
 
 
-
 #endif