diff --git a/src/protocols/HTTP/HTTP.cpp b/src/protocols/HTTP/HTTP.cpp
index 9200acb0..00b046d2 100644
--- a/src/protocols/HTTP/HTTP.cpp
+++ b/src/protocols/HTTP/HTTP.cpp
@@ -140,8 +140,8 @@ int16_t HTTPClient::post(const char* url, const char* content, String& response,
   }
 
   // build the POST request
-  char contentLengthStr[8];
-  itoa(strlen(content), contentLengthStr, 10);
+  char contentLengthStr[12];
+  sprintf(contentLengthStr, "%d", strlen(content));
   char* request = new char[strlen(endpoint) + strlen(host) + strlen(contentType) + strlen(contentLengthStr) + strlen(content) + 64 + 1];
   strcpy(request, "POST ");
   strcat(request, endpoint);