Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 23297)
+++ wp-includes/query.php	(working copy)
@@ -2996,11 +2996,17 @@
 
 			$query = reset( $tax_query_in_and );
 
-			if ( 'term_id' == $query['field'] )
-				$term = get_term( reset( $query['terms'] ), $query['taxonomy'] );
-			elseif ( $query['terms'] )
-				$term = get_term_by( $query['field'], reset( $query['terms'] ), $query['taxonomy'] );
-
+			if ( $this->is_tag ) {
+				$term = get_term( $this->get( 'tag_id' ), 'post_tag' );
+			} else if ( $this->is_category ) {
+				$term = get_term( $this->get( 'cat' ), 'category' );
+			} else {
+				if ( 'term_id' == $query['field'] )
+					$term = get_term( reset( $query['terms'] ), $query['taxonomy'] );
+				else
+					$term = get_term_by( $query['field'], reset( $query['terms'] ), $query['taxonomy'] );
+			}
+			
 			if ( ! empty( $term ) && ! is_wp_error( $term ) )  {
 				$this->queried_object = $term;
 				$this->queried_object_id = (int) $term->term_id;