diff --git a/iris/bi/lib/fractional.v b/iris/bi/lib/fractional.v
index 05dee6eeab90b4479539ed5c8335e4a0431b4aec..ac13b5f7966f79de2b6495d15dc1a7259fd7b701 100644
--- a/iris/bi/lib/fractional.v
+++ b/iris/bi/lib/fractional.v
@@ -14,9 +14,10 @@ Global Arguments AsFractional {_} _%I _%I _%Qp.
 
 Global Arguments fractional {_ _ _} _ _.
 
-Global Hint Mode AsFractional - + - - : typeclass_instances.
+Global Hint Mode AsFractional - ! - - : typeclass_instances.
 (* To make [as_fractional_fractional] a useful instance, we have to
-allow [q] to be an evar. *)
+allow [q] to be an evar. The head of [Φ] will always be a λ so ! is
+not a useful mode there. *)
 Global Hint Mode AsFractional - - + - : typeclass_instances.
 
 Section fractional.