diff --git a/src/Init/Data/List/Basic.lean b/src/Init/Data/List/Basic.lean
index 9008c707b1..8e2efebdd5 100644
--- a/src/Init/Data/List/Basic.lean
+++ b/src/Init/Data/List/Basic.lean
@@ -153,11 +153,11 @@ def dropWhile (p : α → Bool) : List α → List α
   | true  => dropWhile l
   | false =>  a::l
 
-def find (p : α → Bool) : List α → Option α
+def find? (p : α → Bool) : List α → Option α
 | []    => none
 | a::as => match p a with
   | true  => some a
-  | false => find as
+  | false => find? as
 
 def findSome? (f : α → Option β) : List α → Option β
 | []    => none
diff --git a/src/Init/Lean/Util/WHNF.lean b/src/Init/Lean/Util/WHNF.lean
index 149b175c0a..9a3ad4c88c 100644
--- a/src/Init/Lean/Util/WHNF.lean
+++ b/src/Init/Lean/Util/WHNF.lean
@@ -59,7 +59,7 @@ private def toCtorIfLit : Expr → Expr
 
 private def getRecRuleFor (rec : RecursorVal) (major : Expr) : Option RecursorRule :=
 match major.getAppFn with
-| Expr.const fn _ _ => rec.rules.find $ fun r => r.ctor == fn
+| Expr.const fn _ _ => rec.rules.find? $ fun r => r.ctor == fn
 | _                 => none
 
 @[specialize] private def toCtorWhenK {m : Type → Type} [Monad m]