diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-settings-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-settings-controller.php
index 921360e3ee..6d8239793e 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-settings-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-settings-controller.php
@@ -95,6 +95,12 @@ class WP_REST_Settings_Controller extends WP_REST_Controller {
 	 * @return mixed
 	 */
 	protected function prepare_value( $value, $schema ) {
+		// If the value is not a scalar, it's not possible to cast it to
+		// anything.
+		if ( ! is_scalar( $value ) ) {
+			return null;
+		}
+
 		switch ( $schema['type'] ) {
 			case 'string':
 				return (string) $value;
@@ -141,9 +147,29 @@ class WP_REST_Settings_Controller extends WP_REST_Controller {
 				continue;
 			}
 
-			// A null value means reset the option, which is essentially deleting it
-			// from the database and then relying on the default value.
+			/**
+			* A `null` value for an option would have the same effect as
+			* deleting the option from the database, and relying on the
+			* default value.
+			*/
 			if ( is_null( $request[ $name ] ) ) {
+				/**
+				 * A `null` value is returned in the response for any option
+				 * that has a non-scalar value.
+				 *
+				 * To protect clients from accidentally including the `null`
+				 * values from a response object in a request, we do not allow
+				 * options with non-scalar values to be updated to `null`.
+				 * Without this added protection a client could mistakenly
+				 * delete all options that have non-scalar values from the
+				 * database.
+				 */
+				if ( ! is_scalar( get_option( $args['option_name'], false ) ) ) {
+					return new WP_Error(
+						'rest_invalid_stored_value', sprintf( __( 'The %s property has an invalid stored value, and cannot be updated to null.' ), $name ), array( 'status' => 500 )
+					);
+				}
+
 				delete_option( $args['option_name'] );
 			} else {
 				update_option( $args['option_name'], $request[ $name ] );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 1255581d3f..2c5642fc26 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38981';
+$wp_version = '4.7-alpha-38982';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.