diff --git a/esphome/components/api/api_pb2.cpp b/esphome/components/api/api_pb2.cpp
index 02628cd035..ba8bcf3275 100644
--- a/esphome/components/api/api_pb2.cpp
+++ b/esphome/components/api/api_pb2.cpp
@@ -1240,7 +1240,7 @@ void ListEntitiesClimateResponse::calculate_size(ProtoSize &size) const {
   }
   if (!this->supported_custom_presets->empty()) {
     for (const char *it : *this->supported_custom_presets) {
-      size.add_length_force(1, strlen(it));
+      size.add_length_force(2, strlen(it));
     }
   }
   size.add_bool(2, this->disabled_by_default);
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index 394e92b9a7..3b756095a1 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -1610,8 +1610,9 @@ class RepeatedTypeInfo(TypeInfo):
             # Other types need the actual value
             # Special handling for const char* elements
             if self._use_pointer and "const char" in self._container_no_template:
+                field_id_size = self.calculate_field_id_size()
                 o += f"  for (const char *it : {container_ref}) {{\n"
-                o += "    size.add_length_force(1, strlen(it));\n"
+                o += f"    size.add_length_force({field_id_size}, strlen(it));\n"
             else:
                 auto_ref = "" if self._ti_is_bool else "&"
                 o += f"  for (const auto {auto_ref}it : {container_ref}) {{\n"