Issue with using Simulink.I​mportExter​nalCTypes

Hello, I am trying to use Simulink.ImportExternalCtypes function to import my legacy code containing enumeration to Matlab. The imported file has an inclusion of the file containing typedef of primitive data type. However, Matlab throws error#20, for example for the data type bool for _Bool. Please suggest how to make use of 'Defines' with Simulink.ImportExternalCtypes. Thanks.