diff --git a/wp-includes/class-wp.php b/wp-includes/class-wp.php
index 88c1c23de..7ca64697a 100644
--- a/wp-includes/class-wp.php
+++ b/wp-includes/class-wp.php
@@ -272,6 +272,11 @@ class WP {
 			}
 		}
 
+		// Convert urldecoded spaces back into +
+		foreach ( $GLOBALS['wp_taxonomies'] as $taxonomy => $t )
+			if ( $t->query_var && isset( $this->query_vars[$t->query_var] ) )
+				$this->query_vars[$t->query_var] = str_replace( ' ', '+', $this->query_vars[$t->query_var] );
+
 		// Limit publicly queried post_types to those that are publicly_queryable
 		if ( isset( $this->query_vars['post_type']) ) {
 			$queryable_post_types = get_post_types( array('publicly_queryable' => true) );
@@ -603,4 +608,4 @@ class WP_MatchesMapRegex {
 
 }
 
-?>
\ No newline at end of file
+?>
diff --git a/wp-includes/query.php b/wp-includes/query.php
index 2f7f20427..e8354592e 100644
--- a/wp-includes/query.php
+++ b/wp-includes/query.php
@@ -1507,7 +1507,7 @@ class WP_Query {
 					$q[$t->query_var] = wp_basename( $q[$t->query_var] );
 				}
 
-				$term = str_replace( ' ', '+', $q[$t->query_var] );
+				$term = $q[$t->query_var];
 
 				if ( strpos($term, '+') !== false ) {
 					$terms = preg_split( '/[+]+/', $term );