diff --git a/wp-admin/network/site-new.php b/wp-admin/network/site-new.php
index 318c7b4..c70ad9f 100644
--- a/wp-admin/network/site-new.php
+++ b/wp-admin/network/site-new.php
@@ -40,10 +40,11 @@ if ( isset( $_REQUEST['action'] ) && 'add-site' == $_REQUEST['action'] ) {
 		wp_die( __( 'Can’t create an empty site.' ) );
 	}
 
-	$blog   = $_POST['blog'];
-	$domain = '';
-	if ( preg_match( '|^([a-zA-Z0-9-])+$|', $blog['domain'] ) ) {
-		$domain = strtolower( $blog['domain'] );
+	$blog       = $_POST['blog'];
+	$domain     = '';
+	$raw_domain = trim( $blog['domain'] );
+	if ( preg_match( '|^([a-zA-Z0-9-])+$|', $raw_domain ) ) {
+		$domain = strtolower( $raw_domain );
 	}
 
 	// If not a subdomain installation, make sure the domain isn't a reserved word