diff --git a/embassy-stm32/src/timer/mod.rs b/embassy-stm32/src/timer/mod.rs
index 4ffb2a289..b5ced45fe 100644
--- a/embassy-stm32/src/timer/mod.rs
+++ b/embassy-stm32/src/timer/mod.rs
@@ -211,6 +211,7 @@ macro_rules! impl_basic_16bit_timer {
                 use core::convert::TryInto;
                 let f = frequency.0;
                 let timer_f = Self::frequency().0;
+                assert!(f > 0);
                 let pclk_ticks_per_timer_period = timer_f / f;
                 let psc: u16 = unwrap!(((pclk_ticks_per_timer_period - 1) / (1 << 16)).try_into());
                 let arr: u16 = unwrap!((pclk_ticks_per_timer_period / (u32::from(psc) + 1)).try_into());
@@ -255,6 +256,7 @@ macro_rules! impl_32bit_timer {
             fn set_frequency(&mut self, frequency: Hertz) {
                 use core::convert::TryInto;
                 let f = frequency.0;
+                assert!(f > 0);
                 let timer_f = Self::frequency().0;
                 let pclk_ticks_per_timer_period = (timer_f / f) as u64;
                 let psc: u16 = unwrap!(((pclk_ticks_per_timer_period - 1) / (1 << 32)).try_into());