diff --git a/crates/wiggle/test-helpers/examples/tracing.rs b/crates/wiggle/test-helpers/examples/tracing.rs
index 3d08ec45e1..0f06e18509 100644
--- a/crates/wiggle/test-helpers/examples/tracing.rs
+++ b/crates/wiggle/test-helpers/examples/tracing.rs
@@ -36,7 +36,7 @@ impl_errno!(types::Errno, types::GuestErrorConversion);
 /// When the `errors` mapping in witx is non-empty, we need to impl the
 /// types::UserErrorConversion trait that wiggle generates from that mapping.
 impl<'a> types::UserErrorConversion for WasiCtx<'a> {
-    fn errno_from_rich_error(&self, e: RichError) -> Result<types::Errno, String> {
+    fn errno_from_rich_error(&self, e: RichError) -> Result<types::Errno, wiggle::Trap> {
         wiggle::tracing::debug!(
             rich_error = wiggle::tracing::field::debug(&e),
             "error conversion"