diff --git a/src/testing/counted.rs b/src/testing/counted.rs
index 5abcdfa..1ea764a 100644
--- a/src/testing/counted.rs
+++ b/src/testing/counted.rs
@@ -11,6 +11,10 @@ impl<'a> FunctorContext<'a> for TestContextCounted {
     type T = CountedInstance;
 }
 
+impl<'a> FallibleCtx<'a> for TestContextCounted {
+    type Fallible = instances::result::ResultFailOver<Self::T>;
+}
+
 impl<'a> Context<'a> for TestContextCounted {
     type _Tm = Self::T;