diff --git a/hw/bsp/stm32l4/family.cmake b/hw/bsp/stm32l4/family.cmake
index c8397f418..83c51c9bf 100644
--- a/hw/bsp/stm32l4/family.cmake
+++ b/hw/bsp/stm32l4/family.cmake
@@ -107,7 +107,7 @@ function(family_configure_example TARGET)
     )
 
   # Add TinyUSB target and port source
-  family_add_tinyusb(${TARGET} OPT_MCU_$(FAMILY_MCUS))
+  family_add_tinyusb(${TARGET} OPT_MCU_${FAMILY_MCUS})
   target_sources(${TARGET}-tinyusb PUBLIC
     ${TOP}/src/portable/synopsys/dwc2/dcd_dwc2.c
     ${TOP}/src/portable/st/stm32_fsdev/dcd_stm32_fsdev.c