Index: src/wp-includes/user.php
===================================================================
--- src/wp-includes/user.php	(revision 54361)
+++ src/wp-includes/user.php	(working copy)
@@ -3050,15 +3050,22 @@
 		$user_login = $_POST['user_login'];
 	}
 
+	$user_login = trim( wp_unslash( $user_login ) );
+
 	if ( empty( $user_login ) ) {
 		$errors->add( 'empty_username', __( '<strong>Error:</strong> Please enter a username or email address.' ) );
 	} elseif ( strpos( $user_login, '@' ) ) {
-		$user_data = get_user_by( 'email', trim( wp_unslash( $user_login ) ) );
+		$user_data = get_user_by( 'email', $user_login );
+
 		if ( empty( $user_data ) ) {
+			$user_data = get_user_by( 'login', $user_login );
+		}
+
+		if ( empty( $user_data ) ) {
 			$errors->add( 'invalid_email', __( '<strong>Error:</strong> There is no account with that username or email address.' ) );
 		}
 	} else {
-		$user_data = get_user_by( 'login', trim( wp_unslash( $user_login ) ) );
+		$user_data = get_user_by( 'login', $user_login );
 	}
 
 	/**