diff --git a/code/espurna/domoticz.ino b/code/espurna/domoticz.ino
index cd870ae6..fdf84df3 100644
--- a/code/espurna/domoticz.ino
+++ b/code/espurna/domoticz.ino
@@ -72,7 +72,7 @@ template<typename T> void domoticzSend(const char * key, T nvalue, const char *
     unsigned int idx = getSetting(key).toInt();
     if (idx > 0) {
         char payload[128];
-        snprintf(payload, 128, "{\"idx\": %d, \"nvalue\": %s, \"svalue\": \"%s\"}", idx, String(nvalue).c_str(), svalue);
+        snprintf(payload, strlen(payload), "{\"idx\": %d, \"nvalue\": %s, \"svalue\": \"%s\"}", idx, String(nvalue).c_str(), svalue);
         mqttSendRaw(getSetting("dczTopicIn", DOMOTICZ_IN_TOPIC).c_str(), payload);
     }
 }
diff --git a/code/espurna/emon.ino b/code/espurna/emon.ino
index dd5348c8..5c5565c1 100644
--- a/code/espurna/emon.ino
+++ b/code/espurna/emon.ino
@@ -191,11 +191,11 @@ void powerMonitorLoop() {
             #if ENABLE_DOMOTICZ
             {
                 char buffer[20];
-                snprintf_P(buffer, 20, PSTR("%d;%s"), _emonPower, String(energy_delta, 3).c_str());
+                snprintf_P(buffer, strlen(buffer), PSTR("%d;%s"), _emonPower, String(energy_delta, 3).c_str());
                 domoticzSend("dczPowIdx", 0, buffer);
-                snprintf_P(buffer, 20, PSTR("%s"), String(energy_delta, 3).c_str());
+                snprintf_P(buffer, strlen(buffer), PSTR("%s"), String(energy_delta, 3).c_str());
                 domoticzSend("dczEnergyIdx", 0, buffer);
-                snprintf_P(buffer, 20, PSTR("%s"), String(_emonCurrent, 3).c_str());
+                snprintf_P(buffer, strlen(buffer), PSTR("%s"), String(_emonCurrent, 3).c_str());
                 domoticzSend("dczCurrentIdx", 0, buffer);
             }
             #endif
diff --git a/code/espurna/hlw8012.ino b/code/espurna/hlw8012.ino
index d3faf45a..1d3a41ef 100644
--- a/code/espurna/hlw8012.ino
+++ b/code/espurna/hlw8012.ino
@@ -295,13 +295,13 @@ void hlw8012Loop() {
             #if ENABLE_DOMOTICZ
             {
                 char buffer[20];
-                snprintf_P(buffer, 20, PSTR("%d;%s"), _hlwPower, String(energy_delta, 3).c_str());
+                snprintf_P(buffer, strlen(buffer), PSTR("%d;%s"), _hlwPower, String(energy_delta, 3).c_str());
                 domoticzSend("dczPowIdx", 0, buffer);
-                snprintf_P(buffer, 20, PSTR("%s"), String(energy_delta, 3).c_str());
+                snprintf_P(buffer, strlen(buffer), PSTR("%s"), String(energy_delta, 3).c_str());
                 domoticzSend("dczEnergyIdx", 0, buffer);
-                snprintf_P(buffer, 20, PSTR("%d"), _hlwVoltage);
+                snprintf_P(buffer, strlen(buffer), PSTR("%d"), _hlwVoltage);
                 domoticzSend("dczVoltIdx", 0, buffer);
-                snprintf_P(buffer, 20, PSTR("%s"), String(_hlwCurrent).c_str());
+                snprintf_P(buffer, strlen(buffer), PSTR("%s"), String(_hlwCurrent).c_str());
                 domoticzSend("dczCurrentIdx", 0, buffer);
             }
             #endif
diff --git a/code/espurna/web.ino b/code/espurna/web.ino
index 8e881a2a..861b56e6 100644
--- a/code/espurna/web.ino
+++ b/code/espurna/web.ino
@@ -762,7 +762,7 @@ void apiRegister(const char * url, const char * key, apiGetCallbackFunction getF
     // Store it
     web_api_t api;
     char buffer[40];
-    snprintf_P(buffer, 39, PSTR("/api/%s"), url);
+    snprintf_P(buffer, strlen(buffer), PSTR("/api/%s"), url);
     api.url = strdup(buffer);
     api.key = strdup(key);
     api.getFn = getFn;