diff --git a/wp-includes/capabilities-functions.php b/wp-includes/capabilities-functions.php
index 4274fa5383..316b850e7b 100644
--- a/wp-includes/capabilities-functions.php
+++ b/wp-includes/capabilities-functions.php
@@ -471,6 +471,9 @@ function get_role( $role ) {
  * @return WP_Role|null WP_Role object if role is added, null if already exists.
  */
 function add_role( $role, $display_name, $capabilities = array() ) {
+	if ( empty( $role ) ) {
+		return;
+	}
 	return wp_roles()->add_role( $role, $display_name, $capabilities );
 }
 
diff --git a/wp-includes/class-wp-roles.php b/wp-includes/class-wp-roles.php
index 643ee63442..a62c97e65e 100644
--- a/wp-includes/class-wp-roles.php
+++ b/wp-includes/class-wp-roles.php
@@ -172,8 +172,9 @@ class WP_Roles {
 	 * @return WP_Role|void WP_Role object, if role is added.
 	 */
 	public function add_role( $role, $display_name, $capabilities = array() ) {
-		if ( isset( $this->roles[$role] ) )
+		if ( empty( $role ) || isset( $this->roles[ $role ] ) ) {
 			return;
+		}
 
 		$this->roles[$role] = array(
 			'name' => $display_name,
diff --git a/wp-includes/class-wp-user.php b/wp-includes/class-wp-user.php
index 4005a6edc4..971021a759 100644
--- a/wp-includes/class-wp-user.php
+++ b/wp-includes/class-wp-user.php
@@ -439,6 +439,10 @@ class WP_User {
 	 * @param string $role Role name.
 	 */
 	public function add_role( $role ) {
+		if ( empty( $role ) ) {
+			return;
+		}
+
 		$this->caps[$role] = true;
 		update_user_meta( $this->ID, $this->cap_key, $this->caps );
 		$this->get_role_caps();
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 0e11c360f9..733c97a538 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-33966';
+$wp_version = '4.4-alpha-33967';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.