diff --git a/src/Controllers/Version2/class-wc-rest-coupons-v2-controller.php b/src/Controllers/Version2/class-wc-rest-coupons-v2-controller.php
index 7dbcaa1..e8ab107 100644
--- a/src/Controllers/Version2/class-wc-rest-coupons-v2-controller.php
+++ b/src/Controllers/Version2/class-wc-rest-coupons-v2-controller.php
@@ -511,7 +511,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
diff --git a/src/Controllers/Version2/class-wc-rest-customers-v2-controller.php b/src/Controllers/Version2/class-wc-rest-customers-v2-controller.php
index 29d4e07..22fb257 100644
--- a/src/Controllers/Version2/class-wc-rest-customers-v2-controller.php
+++ b/src/Controllers/Version2/class-wc-rest-customers-v2-controller.php
@@ -350,7 +350,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
diff --git a/src/Controllers/Version2/class-wc-rest-order-refunds-v2-controller.php b/src/Controllers/Version2/class-wc-rest-order-refunds-v2-controller.php
index dff06e2..c0b30dc 100644
--- a/src/Controllers/Version2/class-wc-rest-order-refunds-v2-controller.php
+++ b/src/Controllers/Version2/class-wc-rest-order-refunds-v2-controller.php
@@ -410,7 +410,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
@@ -432,13 +432,13 @@ public function get_item_schema() {
 							),
 							'name'         => array(
 								'description' => __( 'Product name.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 								'readonly'    => true,
 							),
 							'product_id'   => array(
 								'description' => __( 'Product ID.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'integer', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 								'readonly'    => true,
 							),
@@ -535,7 +535,7 @@ public function get_item_schema() {
 										),
 										'value' => array(
 											'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-											'type'        => 'mixed',
+											'type'        => array( 'string', 'null' ),
 											'context'     => array( 'view', 'edit' ),
 											'readonly'    => true,
 										),
diff --git a/src/Controllers/Version2/class-wc-rest-orders-v2-controller.php b/src/Controllers/Version2/class-wc-rest-orders-v2-controller.php
index a9422ae..2744e42 100644
--- a/src/Controllers/Version2/class-wc-rest-orders-v2-controller.php
+++ b/src/Controllers/Version2/class-wc-rest-orders-v2-controller.php
@@ -1170,7 +1170,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
@@ -1191,12 +1191,12 @@ public function get_item_schema() {
 							),
 							'name'         => array(
 								'description' => __( 'Product name.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 							'product_id'   => array(
 								'description' => __( 'Product ID.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'integer' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 							'variation_id' => array(
@@ -1282,7 +1282,7 @@ public function get_item_schema() {
 										),
 										'value' => array(
 											'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-											'type'        => 'mixed',
+											'type'        => array( 'string', 'null' ),
 											'context'     => array( 'view', 'edit' ),
 										),
 									),
@@ -1373,7 +1373,7 @@ public function get_item_schema() {
 										),
 										'value' => array(
 											'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-											'type'        => 'mixed',
+											'type'        => array( 'string', 'null' ),
 											'context'     => array( 'view', 'edit' ),
 										),
 									),
@@ -1397,12 +1397,12 @@ public function get_item_schema() {
 							),
 							'method_title' => array(
 								'description' => __( 'Shipping method name.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 							'method_id'    => array(
 								'description' => __( 'Shipping method ID.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 							'instance_id'  => array(
@@ -1464,7 +1464,7 @@ public function get_item_schema() {
 										),
 										'value' => array(
 											'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-											'type'        => 'mixed',
+											'type'        => array( 'string', 'null' ),
 											'context'     => array( 'view', 'edit' ),
 										),
 									),
@@ -1488,7 +1488,7 @@ public function get_item_schema() {
 							),
 							'name'       => array(
 								'description' => __( 'Fee name.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 							'tax_class'  => array(
@@ -1562,7 +1562,7 @@ public function get_item_schema() {
 										),
 										'value' => array(
 											'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-											'type'        => 'mixed',
+											'type'        => array( 'string', 'null' ),
 											'context'     => array( 'view', 'edit' ),
 										),
 									),
@@ -1586,7 +1586,7 @@ public function get_item_schema() {
 							),
 							'code'         => array(
 								'description' => __( 'Coupon code.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 							'discount'     => array(
@@ -1620,7 +1620,7 @@ public function get_item_schema() {
 										),
 										'value' => array(
 											'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-											'type'        => 'mixed',
+											'type'        => array( 'string', 'null' ),
 											'context'     => array( 'view', 'edit' ),
 										),
 									),
diff --git a/src/Controllers/Version2/class-wc-rest-product-variations-v2-controller.php b/src/Controllers/Version2/class-wc-rest-product-variations-v2-controller.php
index 392098a..4941870 100644
--- a/src/Controllers/Version2/class-wc-rest-product-variations-v2-controller.php
+++ b/src/Controllers/Version2/class-wc-rest-product-variations-v2-controller.php
@@ -799,7 +799,7 @@ public function get_item_schema() {
 				),
 				'manage_stock'          => array(
 					'description' => __( 'Stock management at variation level.', 'woocommerce-rest-api' ),
-					'type'        => 'mixed',
+					'type'        => array( 'boolean', 'null' ),
 					'default'     => false,
 					'context'     => array( 'view', 'edit' ),
 				),
@@ -982,7 +982,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
diff --git a/src/Controllers/Version2/class-wc-rest-products-v2-controller.php b/src/Controllers/Version2/class-wc-rest-products-v2-controller.php
index f38ecb7..8155463 100644
--- a/src/Controllers/Version2/class-wc-rest-products-v2-controller.php
+++ b/src/Controllers/Version2/class-wc-rest-products-v2-controller.php
@@ -2084,7 +2084,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
diff --git a/src/Controllers/Version2/class-wc-rest-setting-options-v2-controller.php b/src/Controllers/Version2/class-wc-rest-setting-options-v2-controller.php
index 7c8a72a..e23aa3a 100644
--- a/src/Controllers/Version2/class-wc-rest-setting-options-v2-controller.php
+++ b/src/Controllers/Version2/class-wc-rest-setting-options-v2-controller.php
@@ -530,12 +530,18 @@ public function get_item_schema() {
 				),
 				'value'       => array(
 					'description' => __( 'Setting value.', 'woocommerce-rest-api' ),
-					'type'        => 'mixed',
+					'type'        => array( 'string', 'array', 'null' ),
+					'items'       => array(
+						'type' => array( 'string', 'null' ),
+					),
 					'context'     => array( 'view', 'edit' ),
 				),
 				'default'     => array(
 					'description' => __( 'Default value for the setting.', 'woocommerce-rest-api' ),
-					'type'        => 'mixed',
+					'type'        => array( 'string', 'array', 'null' ),
+					'items'       => array(
+						'type' => array( 'string', 'null' ),
+					),
 					'context'     => array( 'view', 'edit' ),
 					'readonly'    => true,
 				),
diff --git a/src/Controllers/Version3/class-wc-rest-controller.php b/src/Controllers/Version3/class-wc-rest-controller.php
index 5ee0bc4..d851be5 100644
--- a/src/Controllers/Version3/class-wc-rest-controller.php
+++ b/src/Controllers/Version3/class-wc-rest-controller.php
@@ -77,6 +77,35 @@ protected function add_additional_fields_schema( $schema ) {
 		return $schema;
 	}
 
+	/**
+	 * Compatibility functions for WP 5.5, since custom types are not supported anymore.
+	 * See @link https://core.trac.wordpress.org/changeset/48306
+	 *
+	 * @param string $method Optional. HTTP method of the request.
+	 *
+	 * @return array Endpoint arguments.
+	 */
+	public function get_endpoint_args_for_item_schema( $method = WP_REST_Server::CREATABLE ) {
+
+		$endpoint_args = parent::get_endpoint_args_for_item_schema( $method );
+
+		if ( false === strpos( WP_REST_Server::EDITABLE, $method ) ) {
+			return $endpoint_args;
+		}
+
+		foreach ( $endpoint_args as $field_id => $params ) {
+			/**
+			 * Custom types are not supported as of WP 5.5, this translates type => 'date-time' to type => 'string' with format date-time.
+			 */
+			if ( 'date-time' === $params['type'] ) {
+				$endpoint_args[ $field_id ]['type']   = 'string';
+				$endpoint_args[ $field_id ]['format'] = 'date-time';
+			}
+		}
+
+		return $endpoint_args;
+	}
+
 	/**
 	 * Get normalized rest base.
 	 *
diff --git a/src/Controllers/Version3/class-wc-rest-crud-controller.php b/src/Controllers/Version3/class-wc-rest-crud-controller.php
index c12186e..7aaa3af 100644
--- a/src/Controllers/Version3/class-wc-rest-crud-controller.php
+++ b/src/Controllers/Version3/class-wc-rest-crud-controller.php
@@ -91,6 +91,8 @@ public function delete_item_permissions_check( $request ) {
 		return true;
 	}
 
+
+
 	/**
 	 * Get object permalink.
 	 *
diff --git a/src/Controllers/Version3/class-wc-rest-customers-controller.php b/src/Controllers/Version3/class-wc-rest-customers-controller.php
index 65ce592..072fb08 100644
--- a/src/Controllers/Version3/class-wc-rest-customers-controller.php
+++ b/src/Controllers/Version3/class-wc-rest-customers-controller.php
@@ -293,7 +293,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
diff --git a/src/Controllers/Version3/class-wc-rest-product-variations-controller.php b/src/Controllers/Version3/class-wc-rest-product-variations-controller.php
index 0477e81..6c71016 100644
--- a/src/Controllers/Version3/class-wc-rest-product-variations-controller.php
+++ b/src/Controllers/Version3/class-wc-rest-product-variations-controller.php
@@ -736,7 +736,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
diff --git a/src/Controllers/Version3/class-wc-rest-products-controller.php b/src/Controllers/Version3/class-wc-rest-products-controller.php
index a6401bf..6f3d3a0 100644
--- a/src/Controllers/Version3/class-wc-rest-products-controller.php
+++ b/src/Controllers/Version3/class-wc-rest-products-controller.php
@@ -1288,7 +1288,7 @@ public function get_item_schema() {
 							),
 							'value' => array(
 								'description' => __( 'Meta value.', 'woocommerce-rest-api' ),
-								'type'        => 'mixed',
+								'type'        => array( 'string', 'null' ),
 								'context'     => array( 'view', 'edit' ),
 							),
 						),
diff --git a/src/Controllers/Version3/class-wc-rest-setting-options-controller.php b/src/Controllers/Version3/class-wc-rest-setting-options-controller.php
index b725569..59d3828 100644
--- a/src/Controllers/Version3/class-wc-rest-setting-options-controller.php
+++ b/src/Controllers/Version3/class-wc-rest-setting-options-controller.php
@@ -199,12 +199,18 @@ public function get_item_schema() {
 				),
 				'value'       => array(
 					'description' => __( 'Setting value.', 'woocommerce-rest-api' ),
-					'type'        => 'mixed',
+					'type'        => array( 'string', 'array', 'null' ),
+					'items'       => array(
+						'type' => array( 'string', 'null' ),
+					),
 					'context'     => array( 'view', 'edit' ),
 				),
 				'default'     => array(
 					'description' => __( 'Default value for the setting.', 'woocommerce-rest-api' ),
-					'type'        => 'mixed',
+					'type'        => array( 'string', 'array', 'null' ),
+					'items'       => array(
+						'type' => array( 'string', 'null' ),
+					),
 					'context'     => array( 'view', 'edit' ),
 					'readonly'    => true,
 				),