diff --git a/libwvdrmengine/cdm/core/src/cdm_engine.cpp b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
index fd5234f3..132d2e4c 100644
--- a/libwvdrmengine/cdm/core/src/cdm_engine.cpp
+++ b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
@@ -455,6 +455,7 @@ CdmResponseType CdmEngine::RestoreKey(const CdmSessionId& session_id,
 CdmResponseType CdmEngine::RemoveKeys(const CdmSessionId& session_id) {
   LOGI("session_id = %s", IdToString(session_id));
   std::shared_ptr<CdmSession> session;
+  std::unique_lock<std::recursive_mutex> lock(session_map_lock_);
   if (!session_map_.FindSession(session_id, &session)) {
     LOGE("Session not found: session_id = %s", IdToString(session_id));
     return SESSION_NOT_FOUND_5;
@@ -466,6 +467,7 @@ CdmResponseType CdmEngine::RemoveKeys(const CdmSessionId& session_id) {
 CdmResponseType CdmEngine::RemoveLicense(const CdmSessionId& session_id) {
   LOGI("session_id = %s", IdToString(session_id));
   std::shared_ptr<CdmSession> session;
+  std::unique_lock<std::recursive_mutex> lock(session_map_lock_);
   if (!session_map_.FindSession(session_id, &session)) {
     LOGE("Session not found: session_id = %s", IdToString(session_id));
     return SESSION_NOT_FOUND_19;