Index: core/units/helpers/curl_helper.php
===================================================================
--- core/units/helpers/curl_helper.php
+++ core/units/helpers/curl_helper.php
@@ -208,6 +208,8 @@
 				// don't verify SSL certificates
 				CURLOPT_SSL_VERIFYPEER => false,
 				CURLOPT_SSL_VERIFYHOST => false,
+
+				// prevents CURL from adding "Expect: 100-continue" header for POST requests
 				CURLOPT_HTTPHEADER => Array ('Expect:'),
 			);