Index: branches/5.3.x/core/install/step_templates/security.tpl
===================================================================
diff -u -N -r15962 -r15999
--- branches/5.3.x/core/install/step_templates/security.tpl	(.../security.tpl)	(revision 15962)
+++ branches/5.3.x/core/install/step_templates/security.tpl	(.../security.tpl)	(revision 15999)
@@ -48,7 +48,7 @@
 	$curl_helper = $this->Application->recallObject('CurlHelper');
 	/* @var $curl_helper kCurlHelper */
 
-	$result = $curl_helper->Send($this->Application->BaseURL(WRITEBALE_BASE) . 'install_check.php');
+	$result = $curl_helper->Send($this->Application->BaseURL() . ltrim(WRITEBALE_BASE, '/') . '/install_check.php');
 	unlink(WRITEABLE . '/install_check.php');
 	$execute_check = ($result !== 'OK');