diff --git a/sonoff/support.ino b/sonoff/support.ino
index 33841cc26..bb6a6aa72 100644
--- a/sonoff/support.ino
+++ b/sonoff/support.ino
@@ -835,7 +835,7 @@ void SerialSendRaw(char *codes)
 
   int size = strlen(codes);
 
-  while (size > 0) {
+  while (size > 1) {
     strlcpy(stemp, codes, sizeof(stemp));
     code = strtol(stemp, &p, 16);
     Serial.write(code);
diff --git a/sonoff/xdrv_08_serial_bridge.ino b/sonoff/xdrv_08_serial_bridge.ino
index 8a0543858..2604bfebf 100644
--- a/sonoff/xdrv_08_serial_bridge.ino
+++ b/sonoff/xdrv_08_serial_bridge.ino
@@ -126,7 +126,7 @@ void CmndSSerialSend(void)
         char *codes = RemoveSpace(XdrvMailbox.data);
         int size = strlen(XdrvMailbox.data);
 
-        while (size > 0) {
+        while (size > 1) {
           strlcpy(stemp, codes, sizeof(stemp));
           code = strtol(stemp, &p, 16);
           SerialBridgeSerial->write(code);                                  // "AA004566" as hex values
diff --git a/sonoff/xdrv_23_zigbee_9_impl.ino b/sonoff/xdrv_23_zigbee_9_impl.ino
index 69ae1d12b..32d1e8885 100644
--- a/sonoff/xdrv_23_zigbee_9_impl.ino
+++ b/sonoff/xdrv_23_zigbee_9_impl.ino
@@ -291,7 +291,7 @@ void CmndZigbeeZNPSend(void)
 
 		SBuffer buf((size+1)/2);
 
-    while (size > 0) {
+    while (size > 1) {
       char stemp[3];
       strlcpy(stemp, codes, sizeof(stemp));
       code = strtol(stemp, nullptr, 16);