STM32F103 replaced by STM32L151, unable to program

Hello,

I've made a development board and used a STM32F103C8T6 controller. This works fine with a ST-LINK V2 programmer. Actually a simple Blue Pill design.

I've now replaced the STM32F103C8T6 with a STM32L151C8T6 controller with the same pinout. 

Now I cannot program this controller, and I tried every solution the programming software (STM32 ST-LINK Utility) gives.

I think I forget a little adaption on the design for the L controller.

Anyone any experience with programming the STM32L151 and special things to look after when programming?

Thanks in advance, 

Leo

As attachment the schematic of my prototype board.

(I already tried a 390 ohm resistor in serial with the 8MHz crystal, and using the reset of the programmer, both not successful).