getting Exception while saving Customer model

Hi Expert, I am loading the model first. final CustomerModel customerModel = getModelService().get(CustomerModel.class);

Then i am updating one attribute in customer model and then performing

             **modelService.save(customerModel);**

Then i am getting the below exception. Could you please help.

ion is de.hybris.platform.servicelayer.exceptions.ModelSavingException: [de.hybris.platform.servicelayer.interceptor.impl.MandatoryAttributesValidator@4e5db93c]:missing values for [uid] in model CustomerModel () to create a new Customer] with root cause de.hybris.platform.servicelayer.interceptor.InterceptorException: [de.hybris.platform.servicelayer.interceptor.impl.MandatoryAttributesValidator@4e5db93c]:missing values for [uid] in model CustomerModel () to create a new Customer at de.hybris.platform.servicelayer.interceptor.impl.MandatoryAttributesValidator.onValidate(MandatoryAttributesValidator.java:98) at de.hybris.platform.servicelayer.internal.model.impl.wrapper.ModelWrapper.invokeValidateInterceptors(ModelWrapper.java:291) at de.hybris.platform.servicelayer.internal.model.impl.wrapper.ModelWrapper.validate(ModelWrapper.java:239) at de.hybris.platform.servicelayer.internal.model.extractor.impl.DefaultModelExtractor.process(DefaultModelExtractor.java:58) at de.hybris.platform.servicelayer.internal.model.impl.DefaultModelService.performPersistenceOperations(DefaultModelService.java:711) at de.hybris.platform.servicelayer.internal.model.impl.DefaultModelService.saveAllInternal(DefaultModelService.java:706) at de.hybris.platform.servicelayer.internal.model.impl.DefaultModelService.saveAll(DefaultModelService.java:686) at de.hybris.platform.servicelayer.internal.model.impl.DefaultModelService.save(DefaultModelService.java:634) at com.batelco.b2ctelco.storefront.controllers.pages.HomePageController.home(HomePageController.java:88) at sun.reflect.Na