When an application is loaded into a device (100, 200), the device verifies that the application originates from a trusted operator. The verification implies that the application must, in a secure manner, present itself to the device in such a way that the device can ensure that it originates from the trusted operator. The device identifies the trusted operator as well as the issuer of a SIM (211) located in the device. Thereafter, the device compares the identity of the trusted operator with the identity of the issuer of the SIM, and if the identity of the trusted operator corresponds to the identity of the issuer of the SIM, the previously verified application is installed in a secure execution environment (104, 204, 211) of the device.