diff --git a/esphome/components/web_server/web_server.cpp b/esphome/components/web_server/web_server.cpp
index 40830196433..1dda6204fee 100644
--- a/esphome/components/web_server/web_server.cpp
+++ b/esphome/components/web_server/web_server.cpp
@@ -415,7 +415,7 @@ void WebServer::setup() {
   this->set_interval(10000, [this]() {
     char buf[32];
     auto uptime = static_cast<uint32_t>(millis_64() / 1000);
-    buf_append_printf(buf, sizeof(buf), 0, "{\"uptime\":%u}", uptime);
+    buf_append_printf(buf, sizeof(buf), 0, "{\"uptime\":%" PRIu32 "}", uptime);
     this->events_.try_send_nodefer(buf, "ping", millis(), 30000);
   });
 }