diff --git a/esphome/components/sonoff_d1/sonoff_d1.cpp b/esphome/components/sonoff_d1/sonoff_d1.cpp
index e3d55681c5..cd09f31dd7 100644
--- a/esphome/components/sonoff_d1/sonoff_d1.cpp
+++ b/esphome/components/sonoff_d1/sonoff_d1.cpp
@@ -50,7 +50,7 @@ static const char *const TAG = "sonoff_d1";
 
 uint8_t SonoffD1Output::calc_checksum_(const uint8_t *cmd, const size_t len) {
   uint8_t crc = 0;
-  for (int i = 2; i < len - 1; i++) {
+  for (size_t i = 2; i < len - 1; i++) {
     crc += cmd[i];
   }
   return crc;