diff --git a/biometrics/fingerprint/2.1/default/BiometricsFingerprint.cpp b/biometrics/fingerprint/2.1/default/BiometricsFingerprint.cpp
index c6774ca..f687959 100644
--- a/biometrics/fingerprint/2.1/default/BiometricsFingerprint.cpp
+++ b/biometrics/fingerprint/2.1/default/BiometricsFingerprint.cpp
@@ -145,6 +145,7 @@
 
 Return<uint64_t> BiometricsFingerprint::setNotify(
         const sp<IBiometricsFingerprintClientCallback>& clientCallback) {
+    std::lock_guard<std::mutex> lock(mClientCallbackMutex);
     mClientCallback = clientCallback;
     // This is here because HAL 2.1 doesn't have a way to propagate a
     // unique token for its driver. Subsequent versions should send a unique
@@ -259,6 +260,7 @@
 void BiometricsFingerprint::notify(const fingerprint_msg_t *msg) {
     BiometricsFingerprint* thisPtr = static_cast<BiometricsFingerprint*>(
             BiometricsFingerprint::getInstance());
+    std::lock_guard<std::mutex> lock(thisPtr->mClientCallbackMutex);
     if (thisPtr == nullptr || thisPtr->mClientCallback == nullptr) {
         ALOGE("Receiving callbacks before the client callback is registered.");
         return;
diff --git a/biometrics/fingerprint/2.1/default/BiometricsFingerprint.h b/biometrics/fingerprint/2.1/default/BiometricsFingerprint.h
index 5923c84..6d64e3d 100644
--- a/biometrics/fingerprint/2.1/default/BiometricsFingerprint.h
+++ b/biometrics/fingerprint/2.1/default/BiometricsFingerprint.h
@@ -69,6 +69,7 @@
     static FingerprintAcquiredInfo VendorAcquiredFilter(int32_t error, int32_t* vendorCode);
     static BiometricsFingerprint* sInstance;
 
+    std::mutex mClientCallbackMutex;
     sp<IBiometricsFingerprintClientCallback> mClientCallback;
     fingerprint_device_t *mDevice;
 };