diff --git a/include/PowerMeterMqtt.h b/include/PowerMeterMqtt.h
index 5dd01d2c..3786fca6 100644
--- a/include/PowerMeterMqtt.h
+++ b/include/PowerMeterMqtt.h
@@ -3,7 +3,7 @@
 
 #include "PowerMeterProvider.h"
 #include <espMqttClient.h>
-#include <map>
+#include <vector>
 #include <mutex>
 
 class PowerMeterMqtt : public PowerMeterProvider {
@@ -15,14 +15,16 @@ public:
     void doMqttPublish() const final;
 
 private:
-    void onMqttMessage(const espMqttClientTypes::MessageProperties& properties,
-        const char* topic, const uint8_t* payload, size_t len, size_t index, size_t total);
+    using MsgProperties = espMqttClientTypes::MessageProperties;
+    void onMessage(MsgProperties const& properties, char const* topic,
+            uint8_t const* payload, size_t len, size_t index,
+            size_t total, float* targetVariable);
 
     float _powerValueOne = 0;
     float _powerValueTwo = 0;
     float _powerValueThree = 0;
 
-    std::map<String, float*> _mqttSubscriptions;
+    std::vector<String> _mqttSubscriptions;
 
     mutable std::mutex _mutex;
 };
diff --git a/src/PowerMeterMqtt.cpp b/src/PowerMeterMqtt.cpp
index 9a470ccf..1a74f41d 100644
--- a/src/PowerMeterMqtt.cpp
+++ b/src/PowerMeterMqtt.cpp
@@ -6,15 +6,16 @@
 
 bool PowerMeterMqtt::init()
 {
-    auto subscribe = [this](char const* topic, float* target) {
+    auto subscribe = [this](char const* topic, float* targetVariable) {
         if (strlen(topic) == 0) { return; }
         MqttSettings.subscribe(topic, 0,
-                std::bind(&PowerMeterMqtt::onMqttMessage,
+                std::bind(&PowerMeterMqtt::onMessage,
                     this, std::placeholders::_1, std::placeholders::_2,
                     std::placeholders::_3, std::placeholders::_4,
-                    std::placeholders::_5, std::placeholders::_6)
+                    std::placeholders::_5, std::placeholders::_6,
+                    targetVariable)
                 );
-        _mqttSubscriptions.try_emplace(topic, target);
+        _mqttSubscriptions.push_back(topic);
     };
 
     auto const& config = Configuration.get();
@@ -27,32 +28,31 @@ bool PowerMeterMqtt::init()
 
 void PowerMeterMqtt::deinit()
 {
-    for (auto const& s: _mqttSubscriptions) { MqttSettings.unsubscribe(s.first); }
+    for (auto const& t: _mqttSubscriptions) { MqttSettings.unsubscribe(t); }
     _mqttSubscriptions.clear();
 }
 
-void PowerMeterMqtt::onMqttMessage(const espMqttClientTypes::MessageProperties& properties, const char* topic, const uint8_t* payload, size_t len, size_t index, size_t total)
+void PowerMeterMqtt::onMessage(PowerMeterMqtt::MsgProperties const& properties,
+        char const* topic, uint8_t const* payload, size_t len, size_t index,
+        size_t total, float* targetVariable)
 {
-    for (auto const& subscription: _mqttSubscriptions) {
-        if (subscription.first != topic) { continue; }
-
-        std::string value(reinterpret_cast<const char*>(payload), len);
-        try {
-            *subscription.second = std::stof(value);
-        }
-        catch(std::invalid_argument const& e) {
-            MessageOutput.printf("[PowerMeterMqtt] cannot parse payload of topic '%s' as float: %s\r\n",
-                    topic, value.c_str());
-            return;
-        }
-
-        if (_verboseLogging) {
-            MessageOutput.printf("[PowerMeterMqtt] Updated from '%s', TotalPower: %5.2f\r\n",
-                    topic, getPowerTotal());
-        }
-
-        gotUpdate();
+    std::string value(reinterpret_cast<char const*>(payload), len);
+    try {
+        std::lock_guard<std::mutex> l(_mutex);
+        *targetVariable = std::stof(value);
     }
+    catch (std::invalid_argument const& e) {
+        MessageOutput.printf("[PowerMeterMqtt] cannot parse payload of topic "
+                "'%s' as float: %s\r\n", topic, value.c_str());
+        return;
+    }
+
+    if (_verboseLogging) {
+        MessageOutput.printf("[PowerMeterMqtt] Updated from '%s', TotalPower: %5.2f\r\n",
+                topic, getPowerTotal());
+    }
+
+    gotUpdate();
 }
 
 float PowerMeterMqtt::getPowerTotal() const