diff --git a/wp-includes/query.php b/wp-includes/query.php
index 5e2941661..6ce4e5bc1 100644
--- a/wp-includes/query.php
+++ b/wp-includes/query.php
@@ -1692,7 +1692,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['category__in']) ) {
-			$q['category__in'] = array_map('absint', array_unique( $q['category__in'] ) );
+			$q['category__in'] = array_map('absint', array_unique( (array) $q['category__in'] ) );
 			$tax_query[] = array(
 				'taxonomy' => 'category',
 				'terms' => $q['category__in'],
@@ -1701,7 +1701,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['category__not_in']) ) {
-			$q['category__not_in'] = array_map('absint', array_unique( $q['category__not_in'] ) );
+			$q['category__not_in'] = array_map('absint', array_unique( (array) $q['category__not_in'] ) );
 			$tax_query[] = array(
 				'taxonomy' => 'category',
 				'terms' => $q['category__not_in'],
@@ -1710,7 +1710,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['category__and']) ) {
-			$q['category__and'] = array_map('absint', array_unique( $q['category__and'] ) );
+			$q['category__and'] = array_map('absint', array_unique( (array) $q['category__and'] ) );
 			$tax_query[] = array(
 				'taxonomy' => 'category',
 				'terms' => $q['category__and'],
@@ -1729,7 +1729,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['tag__in']) ) {
-			$q['tag__in'] = array_map('absint', array_unique( $q['tag__in'] ) );
+			$q['tag__in'] = array_map('absint', array_unique( (array) $q['tag__in'] ) );
 			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms' => $q['tag__in']
@@ -1737,7 +1737,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['tag__not_in']) ) {
-			$q['tag__not_in'] = array_map('absint', array_unique( $q['tag__not_in'] ) );
+			$q['tag__not_in'] = array_map('absint', array_unique( (array) $q['tag__not_in'] ) );
 			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms' => $q['tag__not_in'],
@@ -1746,7 +1746,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['tag__and']) ) {
-			$q['tag__and'] = array_map('absint', array_unique( $q['tag__and'] ) );
+			$q['tag__and'] = array_map('absint', array_unique( (array) $q['tag__and'] ) );
 			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms' => $q['tag__and'],
@@ -1755,7 +1755,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['tag_slug__in']) ) {
-			$q['tag_slug__in'] = array_map('sanitize_title', $q['tag_slug__in']);
+			$q['tag_slug__in'] = array_map('sanitize_title', (array) $q['tag_slug__in']);
 			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms' => $q['tag_slug__in'],
@@ -1764,7 +1764,7 @@ class WP_Query {
 		}
 
 		if ( !empty($q['tag_slug__and']) ) {
-			$q['tag_slug__and'] = array_map('sanitize_title', $q['tag_slug__and']);
+			$q['tag_slug__and'] = array_map('sanitize_title', (array) $q['tag_slug__and']);
 			$tax_query[] = array(
 				'taxonomy' => 'post_tag',
 				'terms' => $q['tag_slug__and'],