diff --git a/src/wp-includes/pluggable.php b/src/wp-includes/pluggable.php
index c2a975d896456..58527b19a6685 100644
--- a/src/wp-includes/pluggable.php
+++ b/src/wp-includes/pluggable.php
@@ -595,7 +595,9 @@ function wp_mail( $to, $subject, $message, $headers = '', $attachments = array()
 	 */
 	function wp_authenticate( $username, $password ) {
 		$username = sanitize_user( $username );
-		$password = trim( $password );
+		if ( is_string( $password ) && '' !== $password ) {
+			$password = trim( $password );
+		}
 
 		/**
 		 * Filters whether a set of user login credentials are valid.