diff --git a/embassy-stm32/src/rng.rs b/embassy-stm32/src/rng.rs
index a56fba19b..77e408d3d 100644
--- a/embassy-stm32/src/rng.rs
+++ b/embassy-stm32/src/rng.rs
@@ -13,6 +13,7 @@ use crate::peripherals;
 
 pub(crate) static RNG_WAKER: AtomicWaker = AtomicWaker::new();
 
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum Error {
     SeedError,
     ClockError,