diff --git a/src/func/classes/solo.rs b/src/func/classes/solo.rs
index 2a9136e..a2d1112 100644
--- a/src/func/classes/solo.rs
+++ b/src/func/classes/solo.rs
@@ -115,3 +115,13 @@ impl LocalFunctor for SoloClass {
         fa
     }
 }
+
+impl MonadFail<std::convert::Infallible> for SoloClass {
+    fn fail<'a, A: 'a>(e: std::convert::Infallible) -> Self::F<'a, A>
+    where
+        Self: 'a,
+        std::convert::Infallible: 'a,
+    {
+        match e {}
+    }
+}