diff --git a/src/protocols/HTTP/HTTP.cpp b/src/protocols/HTTP/HTTP.cpp
index 6f4cd23d..63b2fe95 100644
--- a/src/protocols/HTTP/HTTP.cpp
+++ b/src/protocols/HTTP/HTTP.cpp
@@ -142,7 +142,7 @@ int16_t HTTPClient::post(const char* url, const char* content, String& response,
 
   // build the POST request
   char contentLengthStr[12];
-  sprintf(contentLengthStr, "%d", strlen(content));
+  sprintf(contentLengthStr, "%u", (uint16_t)strlen(content));
   char* request = new char[strlen(endpoint) + strlen(host) + strlen(contentType) + strlen(contentLengthStr) + strlen(content) + 64 + 1];
   strcpy(request, "POST ");
   strcat(request, endpoint);
diff --git a/src/protocols/HTTP/HTTP.h b/src/protocols/HTTP/HTTP.h
index edc7d6f1..ae9a3888 100644
--- a/src/protocols/HTTP/HTTP.h
+++ b/src/protocols/HTTP/HTTP.h
@@ -19,7 +19,7 @@ class HTTPClient {
 
       \param port Port to be used for HTTP. Defaults to 80.
     */
-    HTTPClient(TransportLayer* tl, uint16_t port = 80);
+    explicit HTTPClient(TransportLayer* tl, uint16_t port = 80);
 
     /*!
       \brief Sends HTTP GET request.