diff --git a/include/verilated.h b/include/verilated.h
index 66ae9ce7d..45ec64d10 100644
--- a/include/verilated.h
+++ b/include/verilated.h
@@ -120,6 +120,7 @@ class VL_CAPABILITY("mutex") VerilatedMutex {
   public:
     VerilatedMutex() {}
     ~VerilatedMutex() {}
+    const VerilatedMutex& operator!() const { return *this; }  // For -fthread_safety
     /// Acquire/lock mutex
     void lock() VL_ACQUIRE() {
         // Try to acquire the lock by spinning.  If the wait is short,