diff --git a/rp2040-hal/src/i2c/controller/eh1_0_async.rs b/rp2040-hal/src/i2c/controller/eh1_0_async.rs
index d30029a09..69e0aae7f 100644
--- a/rp2040-hal/src/i2c/controller/eh1_0_async.rs
+++ b/rp2040-hal/src/i2c/controller/eh1_0_async.rs
@@ -275,6 +275,7 @@ where
                 } else {
                     w.stop().disable();
                 }
+                // Safety: the `.bits()` fields are marked `unsafe` but all bit values are valid
                 unsafe { w.dat().bits(byte) }
             });
         }