diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 961ad2bb8..7ddf5d7c8 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -2114,6 +2114,10 @@ function update_usermeta( $user_id, $meta_key, $meta_value ) {
 
 	if ( is_array($meta_value) || is_object($meta_value) )
 		$meta_value = serialize($meta_value);
+	$meta_value = trim( $meta_value );
+
+	if ( '' == $meta_value )
+		return false;
 
 	$cur = $wpdb->get_row("SELECT * FROM $wpdb->usermeta WHERE user_id = '$user_id' AND meta_key = '$meta_key'");
 	if ( !$cur ) {