Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 20948)
+++ wp-includes/query.php	(working copy)
@@ -2965,10 +2965,16 @@
 
 			$query = reset( $tax_query_in_and );
 
-			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 ( $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 ( $term && ! is_wp_error($term) )  {
 				$this->queried_object = $term;