diff --git a/src/testing/traced.rs b/src/testing/traced.rs
index 5c61990..493a4f3 100644
--- a/src/testing/traced.rs
+++ b/src/testing/traced.rs
@@ -10,6 +10,10 @@ impl<'a> FunctorContext<'a> for TestContextTraced {
     type T = TracedInstance;
 }
 
+impl<'a> FallibleCtx<'a> for TestContextTraced {
+    type Fallible = instances::result::ResultFailOver<Self::T>;
+}
+
 impl<'a> Context<'a> for TestContextTraced {
     type _Tm = Self::T;