diff --git a/hw/bsp/b-l072z-lrwan1/syscfg.yml b/hw/bsp/b-l072z-lrwan1/syscfg.yml
index 6e5f7f2ef8..285cad7603 100644
--- a/hw/bsp/b-l072z-lrwan1/syscfg.yml
+++ b/hw/bsp/b-l072z-lrwan1/syscfg.yml
@@ -61,3 +61,8 @@ syscfg.vals:
     TIMER_0_TIM: 'TIM2'
     TIMER_1_TIM: 'TIM3'
     TIMER_2_TIM: 'TIM21'
+
+# Disable UART for bootloader, otherwise may not fit on flash
+# with default build
+syscfg.vals.BOOT_LOADER:
+    UART_0: 0
diff --git a/hw/bsp/stm32f4discovery/syscfg.yml b/hw/bsp/stm32f4discovery/syscfg.yml
index 3ada839a8b..1a4c30bc38 100644
--- a/hw/bsp/stm32f4discovery/syscfg.yml
+++ b/hw/bsp/stm32f4discovery/syscfg.yml
@@ -60,3 +60,8 @@ syscfg.vals:
     TIMER_0_TIM: 'TIM9'
     TIMER_1_TIM: 'TIM10'
     TIMER_2_TIM: 'TIM11'
+
+# Disable UART for bootloader, otherwise may not fit on flash
+# with default build
+syscfg.vals.BOOT_LOADER:
+    UART_0: 0