diff --git a/src/wp-includes/deprecated.php b/src/wp-includes/deprecated.php
index bde6bdd430..4361412a92 100644
--- a/src/wp-includes/deprecated.php
+++ b/src/wp-includes/deprecated.php
@@ -4101,3 +4101,36 @@ function remove_option_whitelist( $del_options, $options = '' ) {
 
 	return remove_allowed_options( $del_options, $options );
 }
+
+/**
+ * Adds slashes to only string values in an array of values.
+ *
+ * This should be used when preparing data for core APIs that expect slashed data.
+ * This should not be used to escape data going directly into an SQL query.
+ *
+ * @since 5.3.0
+ * @deprecated 5.6.0 Use wp_slash()
+ *
+ * @see wp_slash()
+ *
+ * @param mixed $value Scalar or array of scalars.
+ * @return mixed Slashes $value
+ */
+function wp_slash_strings_only( $value ) {
+	return map_deep( $value, 'addslashes_strings_only' );
+}
+
+/**
+ * Adds slashes only if the provided value is a string.
+ *
+ * @since 5.3.0
+ * @deprecated 5.6.0
+ *
+ * @see wp_slash()
+ *
+ * @param mixed $value
+ * @return mixed
+ */
+function addslashes_strings_only( $value ) {
+	return is_string( $value ) ? addslashes( $value ) : $value;
+}
diff --git a/src/wp-includes/formatting.php b/src/wp-includes/formatting.php
index 1282320057..a9bb603868 100644
--- a/src/wp-includes/formatting.php
+++ b/src/wp-includes/formatting.php
@@ -5545,33 +5545,6 @@ function wp_unslash( $value ) {
 	return stripslashes_deep( $value );
 }
 
-/**
- * Adds slashes to only string values in an array of values.
- *
- * This should be used when preparing data for core APIs that expect slashed data.
- * This should not be used to escape data going directly into an SQL query.
- *
- * @since 5.3.0
- *
- * @param mixed $value Scalar or array of scalars.
- * @return mixed Slashes $value
- */
-function wp_slash_strings_only( $value ) {
-	return map_deep( $value, 'addslashes_strings_only' );
-}
-
-/**
- * Adds slashes only if the provided value is a string.
- *
- * @since 5.3.0
- *
- * @param mixed $value
- * @return mixed
- */
-function addslashes_strings_only( $value ) {
-	return is_string( $value ) ? addslashes( $value ) : $value;
-}
-
 /**
  * Extract and return the first URL from passed content.
  *
diff --git a/src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php b/src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
index f709afa85a..2d69e9e903 100644
--- a/src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
+++ b/src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
@@ -372,7 +372,7 @@ abstract class WP_REST_Meta_Fields {
 			return true;
 		}
 
-		if ( ! update_metadata( $meta_type, $object_id, wp_slash( $meta_key ), wp_slash_strings_only( $value ) ) ) {
+		if ( ! update_metadata( $meta_type, $object_id, wp_slash( $meta_key ), wp_slash( $value ) ) ) {
 			return new WP_Error(
 				'rest_meta_database_error',
 				/* translators: %s: Custom field key. */