diff --git a/src/zm_monitor.h b/src/zm_monitor.h
index 8760fbf3c..f2060af33 100644
--- a/src/zm_monitor.h
+++ b/src/zm_monitor.h
@@ -341,6 +341,7 @@ class Monitor : public std::enable_shared_from_this<Monitor> {
   PullPointSubscriptionBindingProxy proxyEvent;
   void set_credentials(struct soap *soap);
   std::unordered_map<std::string, std::string> alarms;
+  std::mutex   alarms_mutex;
 #endif
    public:
     explicit ONVIF(Monitor *parent_);
diff --git a/src/zm_monitor_onvif.cpp b/src/zm_monitor_onvif.cpp
index 1cac78b3d..caa27ea3d 100644
--- a/src/zm_monitor_onvif.cpp
+++ b/src/zm_monitor_onvif.cpp
@@ -187,7 +187,10 @@ void Monitor::ONVIF::WaitForMessage() {
           // Apparently simple motion events, the value is boolean, but for people detection can be things like isMotion, isPeople
           if (last_value.find("false") == 0) {
             Info("Triggered off ONVIF");
-            alarms.erase(last_topic);
+            {
+              std::unique_lock<std::mutex> lck(alarms_mutex);
+              alarms.erase(last_topic);
+            }
               Debug(1, "ONVIF Alarms Empty: Alarms count is %zu, alarmed is %s, empty is %d ", alarms.size(), alarmed ? "true": "false", alarms.empty());
             if (alarms.empty()) {
               alarmed = false;
@@ -285,6 +288,7 @@ int SOAP_ENV__Fault(struct soap *soap, char *faultcode, char *faultstring, char
 
 void Monitor::ONVIF::SetNoteSet(Event::StringSet &noteSet) {
   #ifdef WITH_GSOAP
+    std::unique_lock<std::mutex> lck(alarms_mutex);
     if (alarms.empty()) return;
 
     std::string note = "";