diff --git a/sensors/common/default/2.X/multihal/tests/fake_subhal/Sensor.cpp b/sensors/common/default/2.X/multihal/tests/fake_subhal/Sensor.cpp
index a0bb67a..d8e292a 100644
--- a/sensors/common/default/2.X/multihal/tests/fake_subhal/Sensor.cpp
+++ b/sensors/common/default/2.X/multihal/tests/fake_subhal/Sensor.cpp
@@ -76,6 +76,7 @@
                                   static_cast<int64_t>(mSensorInfo.minDelay) * 1000,
                                   static_cast<int64_t>(mSensorInfo.maxDelay) * 1000);
 
+    std::unique_lock<std::mutex> lock(mRunMutex);
     if (mSamplingPeriodNs != samplingPeriodNs) {
         mSamplingPeriodNs = samplingPeriodNs;
         // Wake up the 'run' thread to check if a new event should be generated now