diff --git a/packages/js/api/src/framework/transformations/model-transformer-transformation.ts b/packages/js/api/src/framework/transformations/model-transformer-transformation.ts
index f5b53085987..11b85bae761 100644
--- a/packages/js/api/src/framework/transformations/model-transformer-transformation.ts
+++ b/packages/js/api/src/framework/transformations/model-transformer-transformation.ts
@@ -43,6 +43,10 @@ export class ModelTransformerTransformation< T extends Model > implements ModelT
 	 * @template T
 	 */
 	public constructor( property: string, modelClass: ModelConstructor< T >, transformer: ModelTransformer< T > ) {
+		// Developer-friendly error to make sure this doesn't go unnoticed.
+		if (property.includes('_')) {
+			throw new Error('The property must be camelCase');
+		}
 		this.property = property;
 		this.modelClass = modelClass;
 		this.transformer = transformer;
@@ -74,27 +78,12 @@ export class ModelTransformerTransformation< T extends Model > implements ModelT
 	 * @return {*} The transformed properties.
 	 */
 	public toModel( properties: any ): any {
-		let propertyName = this.property;
-		let val = properties[ propertyName ];
-
-		if ( ! val ) {
-			/*
-			 * Properties are defined in snake_case format, but the properties in the models are camelCase.
-			 * Due to how the hydration of the model works, using TypeScript's Partial, the properties object
-			 * might have been transformed from snake_case to camelCase already, so we try to convert
-			 * the property name to camelCase before giving up.
-			 */
-			propertyName = propertyName.toLowerCase().replace(/[^a-zA-Z0-9]+(.)/g, function (_match, chr) {
-				return chr.toUpperCase();
-			});
-			val = properties[ propertyName ];
-		}
-
+		const val = properties[ this.property ];
 		if ( val ) {
 			if ( Array.isArray( val ) ) {
-				properties[ propertyName ] = val.map( ( v ) => this.transformer.toModel( this.modelClass, v ) );
+				properties[ this.property ] = val.map( ( v ) => this.transformer.toModel( this.modelClass, v ) );
 			} else {
-				properties[ propertyName ] = this.transformer.toModel( this.modelClass, val );
+				properties[ this.property ] = this.transformer.toModel( this.modelClass, val );
 			}
 		}
 
diff --git a/packages/js/api/src/repositories/rest/orders/transformer.ts b/packages/js/api/src/repositories/rest/orders/transformer.ts
index 78f6a327ea6..e050506199f 100644
--- a/packages/js/api/src/repositories/rest/orders/transformer.ts
+++ b/packages/js/api/src/repositories/rest/orders/transformer.ts
@@ -30,13 +30,13 @@ export function createOrderTransformer(): ModelTransformer< Order > {
 			new IgnorePropertyTransformation( [ 'date_created', 'date_modified' ] ),
 			new ModelTransformerTransformation( 'billing', BillingOrderAddress, createBillingAddressTransformer() ),
 			new ModelTransformerTransformation( 'shipping', ShippingOrderAddress, createShippingAddressTransformer() ),
-			new ModelTransformerTransformation( 'tax_lines', OrderTaxRate, createOrderTaxRateTransformer() ),
+			new ModelTransformerTransformation( 'taxLines', OrderTaxRate, createOrderTaxRateTransformer() ),
 			new ModelTransformerTransformation( 'refunds', OrderRefundLine, createOrderRefundLineTransformer() ),
-			new ModelTransformerTransformation( 'coupon_lines', OrderCouponLine, createOrdeCouponLineTransformer() ),
-			new ModelTransformerTransformation( 'fee_lines', OrderFeeLine, createOrderFeeLineTransformer() ),
-			new ModelTransformerTransformation( 'line_items', OrderLineItem, createOrderLineItemTransformer() ),
-			new ModelTransformerTransformation( 'shipping_lines', OrderShippingLine, createOrderShippingItemTransformer() ),
-			new ModelTransformerTransformation( 'meta_data', MetaData, createMetaDataTransformer() ),
+			new ModelTransformerTransformation( 'couponLines', OrderCouponLine, createOrdeCouponLineTransformer() ),
+			new ModelTransformerTransformation( 'feeLines', OrderFeeLine, createOrderFeeLineTransformer() ),
+			new ModelTransformerTransformation( 'lineItems', OrderLineItem, createOrderLineItemTransformer() ),
+			new ModelTransformerTransformation( 'shippingLines', OrderShippingLine, createOrderShippingItemTransformer() ),
+			new ModelTransformerTransformation( 'metaData', MetaData, createMetaDataTransformer() ),
 
 			new PropertyTypeTransformation(
 				{
@@ -212,7 +212,7 @@ function createOrderRefundLineTransformer(): ModelTransformer< OrderRefundLine >
 function createOrdeCouponLineTransformer(): ModelTransformer< OrderCouponLine > {
 	return new ModelTransformer(
 		[
-			new ModelTransformerTransformation( 'meta_data', MetaData, createMetaDataTransformer() ),
+			new ModelTransformerTransformation( 'metaData', MetaData, createMetaDataTransformer() ),
 			new PropertyTypeTransformation(
 				{
 					code: PropertyType.String,