diff --git a/wp-includes/rest-api.php b/wp-includes/rest-api.php
index d59f570c02..8e48f892f7 100644
--- a/wp-includes/rest-api.php
+++ b/wp-includes/rest-api.php
@@ -998,6 +998,9 @@ function rest_validate_value_from_schema( $value, $args, $param = '' ) {
 		if ( ! is_array( $value ) ) {
 			$value = preg_split( '/[\s,]+/', $value );
 		}
+		if ( ! wp_is_numeric_array( $value ) ) {
+			return new WP_Error( 'rest_invalid_param', sprintf( /* translators: 1: parameter, 2: type name */ __( '%1$s is not of type %2$s.' ), $param, 'array' ) );
+		}
 		foreach ( $value as $index => $v ) {
 			$is_valid = rest_validate_value_from_schema( $v, $args['items'], $param . '[' . $index . ']' );
 			if ( is_wp_error( $is_valid ) ) {
@@ -1107,6 +1110,9 @@ function rest_sanitize_value_from_schema( $value, $args ) {
 		foreach ( $value as $index => $v ) {
 			$value[ $index ] = rest_sanitize_value_from_schema( $v, $args['items'] );
 		}
+		// Normalize to numeric array so nothing unexpected
+		// is in the keys.
+		$value = array_values( $value );
 		return $value;
 	}
 	if ( 'integer' === $args['type'] ) {
@@ -1140,5 +1146,9 @@ function rest_sanitize_value_from_schema( $value, $args ) {
 		}
 	}
 
+	if ( 'string' === $args['type'] ) {
+		return strval( $value );
+	}
+
 	return $value;
 }
diff --git a/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php b/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
index e48a307a51..c4200a68d2 100644
--- a/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
+++ b/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
@@ -84,7 +84,7 @@ abstract class WP_REST_Meta_Fields {
 			$response[ $name ] = $value;
 		}
 
-		return (object) $response;
+		return $response;
 	}
 
 	/**
@@ -133,10 +133,24 @@ abstract class WP_REST_Meta_Fields {
 			 */
 			if ( is_null( $request[ $name ] ) ) {
 				$result = $this->delete_meta_value( $object_id, $name );
-			} elseif ( $args['single'] ) {
-				$result = $this->update_meta_value( $object_id, $name, $request[ $name ] );
+				if ( is_wp_error( $result ) ) {
+					return $result;
+				}
+				continue;
+			}
+
+			$is_valid = rest_validate_value_from_schema( $request[ $name ], $args['schema'], 'meta.' . $name );
+			if ( is_wp_error( $is_valid ) ) {
+				$is_valid->add_data( array( 'status' => 400 ) );
+				return $is_valid;
+			}
+
+			$value = rest_sanitize_value_from_schema( $request[ $name ], $args['schema'] );
+
+			if ( $args['single'] ) {
+				$result = $this->update_meta_value( $object_id, $name, $value );
 			} else {
-				$result = $this->update_multi_meta_value( $object_id, $name, $request[ $name ] );
+				$result = $this->update_multi_meta_value( $object_id, $name, $value );
 			}
 
 			if ( is_wp_error( $result ) ) {
@@ -319,12 +333,13 @@ abstract class WP_REST_Meta_Fields {
 			$default_args = array(
 				'name'             => $name,
 				'single'           => $args['single'],
+				'type'             => ! empty( $args['type'] ) ? $args['type'] : null,
 				'schema'           => array(),
 				'prepare_callback' => array( $this, 'prepare_value' ),
 			);
 
 			$default_schema = array(
-				'type'        => null,
+				'type'        => $default_args['type'],
 				'description' => empty( $args['description'] ) ? '' : $args['description'],
 				'default'     => isset( $args['default'] ) ? $args['default'] : null,
 			);
@@ -332,20 +347,18 @@ abstract class WP_REST_Meta_Fields {
 			$rest_args = array_merge( $default_args, $rest_args );
 			$rest_args['schema'] = array_merge( $default_schema, $rest_args['schema'] );
 
-			if ( empty( $rest_args['schema']['type'] ) ) {
-				// Skip over meta fields that don't have a defined type.
-				if ( empty( $args['type'] ) ) {
-					continue;
-				}
+			$type = ! empty( $rest_args['type'] ) ? $rest_args['type'] : null;
+			$type = ! empty( $rest_args['schema']['type'] ) ? $rest_args['schema']['type'] : $type;
 
-				if ( $rest_args['single'] ) {
-					$rest_args['schema']['type'] = $args['type'];
-				} else {
-					$rest_args['schema']['type'] = 'array';
-					$rest_args['schema']['items'] = array(
-						'type' => $args['type'],
-					);
-				}
+			if ( ! in_array( $type, array( 'string', 'boolean', 'integer', 'number' ) ) ) {
+				continue;
+			}
+
+			if ( empty( $rest_args['single'] ) ) {
+				$rest_args['schema']['items'] = array(
+					'type' => $rest_args['type'],
+				);
+				$rest_args['schema']['type'] = 'array';
 			}
 
 			$registered[ $rest_args['name'] ] = $rest_args;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index cf79be638f..8a8747bde7 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-beta3-39221';
+$wp_version = '4.7-beta3-39222';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.