Index: src/wp-includes/class-wp-meta-query.php
===================================================================
--- src/wp-includes/class-wp-meta-query.php	(revision 49803)
+++ src/wp-includes/class-wp-meta-query.php	(working copy)
@@ -560,9 +560,9 @@
 				$join .= $i ? " AS $alias" : '';
 
 				if ( 'LIKE' === $meta_compare_key ) {
-					$join .= $wpdb->prepare( " ON ($this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column AND $alias.meta_key LIKE %s )", '%' . $wpdb->esc_like( $clause['key'] ) . '%' );
+					$join .= $wpdb->prepare( " ON ( $this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column AND $alias.meta_key LIKE %s )", '%' . $wpdb->esc_like( $clause['key'] ) . '%' );
 				} else {
-					$join .= $wpdb->prepare( " ON ($this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column AND $alias.meta_key = %s )", $clause['key'] );
+					$join .= $wpdb->prepare( " ON ( $this->primary_table.$this->primary_id_column = $alias.$this->meta_id_column AND $alias.meta_key = %s )", $clause['key'] );
 				}
 
 				// All other JOIN clauses.