diff --git a/src/nvim/testdir/runtest.vim b/src/nvim/testdir/runtest.vim
index ce7d3b7ee4..82bc1f6950 100644
--- a/src/nvim/testdir/runtest.vim
+++ b/src/nvim/testdir/runtest.vim
@@ -77,7 +77,7 @@ set nomore
 lang mess C
 
 " Always use forward slashes.
-" set shellslash
+set shellslash
 
 " Prepare for calling test_garbagecollect_now().
 let v:testing = 1