diff --git a/esphome/components/web_server_idf/web_server_idf.cpp b/esphome/components/web_server_idf/web_server_idf.cpp
index f37c949e0c..fae0fce6f6 100644
--- a/esphome/components/web_server_idf/web_server_idf.cpp
+++ b/esphome/components/web_server_idf/web_server_idf.cpp
@@ -246,8 +246,8 @@ void AsyncWebServerRequest::redirect(const std::string &url) {
 }
 
 void AsyncWebServerRequest::init_response_(AsyncWebServerResponse *rsp, int code, const char *content_type) {
-  // Set status code - use constants for common codes to avoid string allocation
-  const char *status = nullptr;
+  // Set status code - use constants for common codes, default to 500 for unknown codes
+  const char *status;
   switch (code) {
     case 200:
       status = HTTPD_200;
@@ -259,9 +259,10 @@ void AsyncWebServerRequest::init_response_(AsyncWebServerResponse *rsp, int code
       status = HTTPD_409;
       break;
     default:
+      status = HTTPD_500;
       break;
   }
-  httpd_resp_set_status(*this, status == nullptr ? to_string(code).c_str() : status);
+  httpd_resp_set_status(*this, status);
 
   if (content_type && *content_type) {
     httpd_resp_set_type(*this, content_type);