diff --git a/lib/HaskellLib_H.thy b/lib/HaskellLib_H.thy
index aa5c088ff..945e12c5a 100644
--- a/lib/HaskellLib_H.thy
+++ b/lib/HaskellLib_H.thy
@@ -23,7 +23,7 @@ begin
 abbreviation (input) "flip \<equiv> swp"
 
 abbreviation(input) bind_drop :: "('a, 'c) nondet_monad \<Rightarrow> ('a, 'b) nondet_monad
-                      \<Rightarrow> ('a, 'b) nondet_monad" (infixl ">>_" 60)
+                      \<Rightarrow> ('a, 'b) nondet_monad" (infixl ">>'_" 60)
   where "bind_drop \<equiv> (\<lambda>x y. bind x (K_bind y))"
 
 lemma bind_drop_test: