diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php
index cf131adb67..6540c52fdf 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php
@@ -867,6 +867,7 @@ class WP_REST_Terms_Controller extends WP_REST_Controller {
 			'description'       => __( 'Whether to hide resources not assigned to any posts.' ),
 			'type'              => 'boolean',
 			'default'           => false,
+			'sanitize_callback' => 'rest_sanitize_request_arg',
 			'validate_callback' => 'rest_validate_request_arg',
 		);
 		if ( $taxonomy->hierarchical ) {
diff --git a/tests/phpunit/tests/rest-api/rest-categories-controller.php b/tests/phpunit/tests/rest-api/rest-categories-controller.php
index c62bc695ac..ac2d0f1aa3 100644
--- a/tests/phpunit/tests/rest-api/rest-categories-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-categories-controller.php
@@ -92,6 +92,12 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 		$this->assertEquals( 2, count( $data ) );
 		$this->assertEquals( 'Season 5', $data[0]['name'] );
 		$this->assertEquals( 'The Be Sharps', $data[1]['name'] );
+
+		// Confirm the empty category "Uncategorized" category appears.
+		$request->set_param( 'hide_empty', 'false' );
+		$response = $this->server->dispatch( $request );
+		$data = $response->get_data();
+		$this->assertEquals( 3, count( $data ) );
 	}
 
 	public function test_get_items_parent_zero_arg() {