diff --git a/include/PowerMeterSml.h b/include/PowerMeterSml.h
index 2e180c574..a0d614201 100644
--- a/include/PowerMeterSml.h
+++ b/include/PowerMeterSml.h
@@ -3,6 +3,7 @@
 
 #include <list>
 #include <mutex>
+#include <optional>
 #include <stdint.h>
 #include <Arduino.h>
 #include <HTTPClient.h>
@@ -25,38 +26,43 @@ class PowerMeterSml : public PowerMeterProvider {
     std::string _user;
     mutable std::mutex _mutex;
 
-    float _activePowerTotal = 0.0;
-    float _activePowerL1 = 0.0;
-    float _activePowerL2 = 0.0;
-    float _activePowerL3 = 0.0;
-    float _voltageL1 = 0.0;
-    float _voltageL2 = 0.0;
-    float _voltageL3 = 0.0;
-    float _currentL1 = 0.0;
-    float _currentL2 = 0.0;
-    float _currentL3 = 0.0;
-    float _energyImport = 0.0;
-    float _energyExport = 0.0;
-
-    typedef struct {
+    using values_t = struct {
+        std::optional<float> activePowerTotal = std::nullopt;
+        std::optional<float> activePowerL1 = std::nullopt;
+        std::optional<float> activePowerL2 = std::nullopt;
+        std::optional<float> activePowerL3 = std::nullopt;
+        std::optional<float> voltageL1 = std::nullopt;
+        std::optional<float> voltageL2 = std::nullopt;
+        std::optional<float> voltageL3 = std::nullopt;
+        std::optional<float> currentL1 = std::nullopt;
+        std::optional<float> currentL2 = std::nullopt;
+        std::optional<float> currentL3 = std::nullopt;
+        std::optional<float> energyImport = std::nullopt;
+        std::optional<float> energyExport = std::nullopt;
+    };
+
+    values_t _values;
+    values_t _cache;
+
+    using OBISHandler = struct {
         uint8_t const OBIS[6];
         void (*decoder)(float&);
-        float* target;
+        std::optional<float>* target;
         char const* name;
-    } OBISHandler;
+    };
 
     const std::list<OBISHandler> smlHandlerList{
-        {{0x01, 0x00, 0x10, 0x07, 0x00, 0xff}, &smlOBISW, &_activePowerTotal, "active power total"},
-        {{0x01, 0x00, 0x24, 0x07, 0x00, 0xff}, &smlOBISW, &_activePowerL1, "active power L1"},
-        {{0x01, 0x00, 0x38, 0x07, 0x00, 0xff}, &smlOBISW, &_activePowerL2, "active power L2"},
-        {{0x01, 0x00, 0x4c, 0x07, 0x00, 0xff}, &smlOBISW, &_activePowerL3, "active power L3"},
-        {{0x01, 0x00, 0x20, 0x07, 0x00, 0xff}, &smlOBISVolt, &_voltageL1, "voltage L1"},
-        {{0x01, 0x00, 0x34, 0x07, 0x00, 0xff}, &smlOBISVolt, &_voltageL2, "voltage L2"},
-        {{0x01, 0x00, 0x48, 0x07, 0x00, 0xff}, &smlOBISVolt, &_voltageL3, "voltage L3"},
-        {{0x01, 0x00, 0x1f, 0x07, 0x00, 0xff}, &smlOBISAmpere, &_currentL1, "current L1"},
-        {{0x01, 0x00, 0x33, 0x07, 0x00, 0xff}, &smlOBISAmpere, &_currentL2, "current L2"},
-        {{0x01, 0x00, 0x47, 0x07, 0x00, 0xff}, &smlOBISAmpere, &_currentL3, "current L3"},
-        {{0x01, 0x00, 0x01, 0x08, 0x00, 0xff}, &smlOBISWh, &_energyImport, "energy import"},
-        {{0x01, 0x00, 0x02, 0x08, 0x00, 0xff}, &smlOBISWh, &_energyExport, "energy export"}
+        {{0x01, 0x00, 0x10, 0x07, 0x00, 0xff}, &smlOBISW, &_cache.activePowerTotal, "active power total"},
+        {{0x01, 0x00, 0x24, 0x07, 0x00, 0xff}, &smlOBISW, &_cache.activePowerL1, "active power L1"},
+        {{0x01, 0x00, 0x38, 0x07, 0x00, 0xff}, &smlOBISW, &_cache.activePowerL2, "active power L2"},
+        {{0x01, 0x00, 0x4c, 0x07, 0x00, 0xff}, &smlOBISW, &_cache.activePowerL3, "active power L3"},
+        {{0x01, 0x00, 0x20, 0x07, 0x00, 0xff}, &smlOBISVolt, &_cache.voltageL1, "voltage L1"},
+        {{0x01, 0x00, 0x34, 0x07, 0x00, 0xff}, &smlOBISVolt, &_cache.voltageL2, "voltage L2"},
+        {{0x01, 0x00, 0x48, 0x07, 0x00, 0xff}, &smlOBISVolt, &_cache.voltageL3, "voltage L3"},
+        {{0x01, 0x00, 0x1f, 0x07, 0x00, 0xff}, &smlOBISAmpere, &_cache.currentL1, "current L1"},
+        {{0x01, 0x00, 0x33, 0x07, 0x00, 0xff}, &smlOBISAmpere, &_cache.currentL2, "current L2"},
+        {{0x01, 0x00, 0x47, 0x07, 0x00, 0xff}, &smlOBISAmpere, &_cache.currentL3, "current L3"},
+        {{0x01, 0x00, 0x01, 0x08, 0x00, 0xff}, &smlOBISWh, &_cache.energyImport, "energy import"},
+        {{0x01, 0x00, 0x02, 0x08, 0x00, 0xff}, &smlOBISWh, &_cache.energyExport, "energy export"}
     };
 };
diff --git a/src/PowerMeterSml.cpp b/src/PowerMeterSml.cpp
index 105d20f9d..021b48cd6 100644
--- a/src/PowerMeterSml.cpp
+++ b/src/PowerMeterSml.cpp
@@ -5,23 +5,29 @@
 float PowerMeterSml::getPowerTotal() const
 {
     std::lock_guard<std::mutex> l(_mutex);
-    return _activePowerTotal;
+    if (_values.activePowerTotal.has_value()) { return *_values.activePowerTotal; }
+    return 0;
 }
 
 void PowerMeterSml::doMqttPublish() const
 {
+#define PUB(t, m) \
+    if (_values.m.has_value()) { mqttPublish(t, *_values.m); }
+
     std::lock_guard<std::mutex> l(_mutex);
-    mqttPublish("power1", _activePowerL1);
-    mqttPublish("power2", _activePowerL2);
-    mqttPublish("power3", _activePowerL3);
-    mqttPublish("voltage1", _voltageL1);
-    mqttPublish("voltage2", _voltageL2);
-    mqttPublish("voltage3", _voltageL3);
-    mqttPublish("current1", _currentL1);
-    mqttPublish("current2", _currentL2);
-    mqttPublish("current3", _currentL3);
-    mqttPublish("import", _energyImport);
-    mqttPublish("export", _energyExport);
+    PUB("power1", activePowerL1);
+    PUB("power2", activePowerL2);
+    PUB("power3", activePowerL3);
+    PUB("voltage1", voltageL1);
+    PUB("voltage2", voltageL2);
+    PUB("voltage3", voltageL3);
+    PUB("current1", currentL1);
+    PUB("current2", currentL2);
+    PUB("current3", currentL3);
+    PUB("import", energyImport);
+    PUB("export", energyExport);
+
+#undef PUB
 }
 
 void PowerMeterSml::processSmlByte(uint8_t byte)
@@ -31,22 +37,27 @@ void PowerMeterSml::processSmlByte(uint8_t byte)
             for (auto& handler: smlHandlerList) {
                 if (!smlOBISCheck(handler.OBIS)) { continue; }
 
-                gotUpdate();
-
-                std::lock_guard<std::mutex> l(_mutex);
-                handler.decoder(*handler.target);
+                float helper = 0.0;
+                handler.decoder(helper);
 
                 if (_verboseLogging) {
                     MessageOutput.printf("[%s] decoded %s to %.2f\r\n",
-                            _user.c_str(), handler.name, *handler.target);
+                            _user.c_str(), handler.name, helper);
                 }
+
+                std::lock_guard<std::mutex> l(_mutex);
+                *handler.target = helper;
             }
             break;
         case SML_FINAL:
+            gotUpdate();
+            _values = _cache;
+            _cache = { std::nullopt };
             MessageOutput.printf("[%s] TotalPower: %5.2f\r\n",
                     _user.c_str(), getPowerTotal());
             break;
         case SML_CHECKSUM_ERROR:
+            _cache = { std::nullopt };
             MessageOutput.printf("[%s] checksum verification failed\r\n",
                     _user.c_str());
             break;