diff --git a/wled00/json.cpp b/wled00/json.cpp
index 6fc0e979..c85324d7 100644
--- a/wled00/json.cpp
+++ b/wled00/json.cpp
@@ -980,8 +980,8 @@ void serializeModeData(JsonArray fxdata)
 {
   char lineBuffer[256];
   for (size_t i = 0; i < strip.getModeCount(); i++) {
-    strncpy_P(lineBuffer, strip.getModeData(i), 255);
-    lineBuffer[255] = '\0'; // terminate string
+    strncpy_P(lineBuffer, strip.getModeData(i), sizeof(lineBuffer)/sizeof(char)-1);
+    lineBuffer[sizeof(lineBuffer)/sizeof(char)-1] = '\0'; // terminate string
     if (lineBuffer[0] != 0) {
       char* dataPtr = strchr(lineBuffer,'@');
       if (dataPtr) fxdata.add(dataPtr+1);
@@ -996,8 +996,8 @@ void serializeModeNames(JsonArray arr)
 {
   char lineBuffer[256];
   for (size_t i = 0; i < strip.getModeCount(); i++) {
-    strncpy_P(lineBuffer, strip.getModeData(i), 255);
-    lineBuffer[255] = '\0'; // terminate string
+    strncpy_P(lineBuffer, strip.getModeData(i), sizeof(lineBuffer)/sizeof(char)-1);
+    lineBuffer[sizeof(lineBuffer)/sizeof(char)-1] = '\0'; // terminate string
     if (lineBuffer[0] != 0) {
       char* dataPtr = strchr(lineBuffer,'@');
       if (dataPtr) *dataPtr = 0; // terminate mode data after name
diff --git a/wled00/util.cpp b/wled00/util.cpp
index 220b4773..3c58bf9c 100644
--- a/wled00/util.cpp
+++ b/wled00/util.cpp
@@ -233,8 +233,8 @@ uint8_t extractModeName(uint8_t mode, const char *src, char *dest, uint8_t maxLe
     if (mode < strip.getModeCount()) {
       char lineBuffer[256];
       //strcpy_P(lineBuffer, (const char*)pgm_read_dword(&(WS2812FX::_modeData[mode])));
-      strncpy_P(lineBuffer, strip.getModeData(mode), 255);
-      lineBuffer[255] = '\0'; // terminate string
+      strncpy_P(lineBuffer, strip.getModeData(mode), sizeof(lineBuffer)/sizeof(char)-1);
+      lineBuffer[sizeof(lineBuffer)/sizeof(char)-1] = '\0'; // terminate string
       size_t len = strlen(lineBuffer);
       size_t j = 0;
       for (; j < maxLen && j < len; j++) {
@@ -357,8 +357,8 @@ int16_t extractModeDefaults(uint8_t mode, const char *segVar)
 {
   if (mode < strip.getModeCount()) {
     char lineBuffer[256];
-    strncpy_P(lineBuffer, strip.getModeData(mode), 255);
-    lineBuffer[255] = '\0'; // terminate string
+    strncpy_P(lineBuffer, strip.getModeData(mode), sizeof(lineBuffer)/sizeof(char)-1);
+    lineBuffer[sizeof(lineBuffer)/sizeof(char)-1] = '\0'; // terminate string
     if (lineBuffer[0] != 0) {
       char* startPtr = strrchr(lineBuffer, ';'); // last ";" in FX data
       if (!startPtr) return -1;