diff --git a/ports/stm32/timer.c b/ports/stm32/timer.c
index b4fa1d6cf9..5319ae4ece 100644
--- a/ports/stm32/timer.c
+++ b/ports/stm32/timer.c
@@ -507,7 +507,7 @@ STATIC mp_int_t compute_ticks_from_dtg(uint32_t dtg) {
 }
 
 STATIC void config_deadtime(pyb_timer_obj_t *self, mp_int_t ticks, mp_int_t brk) {
-    TIM_BreakDeadTimeConfigTypeDef deadTimeConfig;
+    TIM_BreakDeadTimeConfigTypeDef deadTimeConfig = {0};
     deadTimeConfig.OffStateRunMode = TIM_OSSR_DISABLE;
     deadTimeConfig.OffStateIDLEMode = TIM_OSSI_DISABLE;
     deadTimeConfig.LockLevel = TIM_LOCKLEVEL_OFF;