1 files changed, 2 insertions, 2 deletions
diff --git a/src/library/scala/collection/immutable/RedBlackTree.scala b/src/library/scala/collection/immutable/RedBlackTree.scala
index 7e8cfcc902..afb4c9c552 100644
--- a/src/library/scala/collection/immutable/RedBlackTree.scala
+++ b/src/library/scala/collection/immutable/RedBlackTree.scala
@@ -409,11 +409,11 @@ object RedBlackTree {
 
     def cons[B](x: B, xs: NList[B]): NList[B] = new NList(x, xs)
 
-    def foldLeft[A, B](xs: NList[A], z: B)(f: (B, A) => B): B = {
+    def foldLeft[A, B](xs: NList[A], z: B)(op: (B, A) => B): B = {
       var acc = z
       var these = xs
       while (these ne null) {
-        acc = f(acc, these.head)
+        acc = op(acc, these.head)
         these = these.tail
       }
       acc