diff --git a/wp-includes/query.php b/wp-includes/query.php
index 92fbb4febd..ecebd221c5 100644
--- a/wp-includes/query.php
+++ b/wp-includes/query.php
@@ -1891,6 +1891,11 @@ class WP_Query {
 			}
 		}
 
+		// If querystring 'cat' is an array, implode it.
+		if ( is_array( $q['cat'] ) ) {
+			$q['cat'] = implode( ',', $q['cat'] );
+		}
+
 		// Category stuff
 		if ( ! empty( $q['cat'] ) && ! $this->is_singular ) {
 			$cat_in = $cat_not_in = array();
@@ -1966,6 +1971,11 @@ class WP_Query {
 			);
 		}
 
+		// If querystring 'tag' is array, implode it.
+		if ( is_array( $q['tag'] ) ) {
+			$q['tag'] = implode( ',', $q['tag'] );
+		}
+
 		// Tag stuff
 		if ( '' != $q['tag'] && !$this->is_singular && $this->query_vars_changed ) {
 			if ( strpos($q['tag'], ',') !== false ) {
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 96b3f388b5..d3e901f8b1 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-33723';
+$wp_version = '4.4-alpha-33724';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.