diff --git a/src/testdir/test17.in b/src/testdir/test17.in
index 3a0a9bb..59b57c2 100644
--- a/src/testdir/test17.in
+++ b/src/testdir/test17.in
@@ -9,13 +9,7 @@
 :else
 : set isfname=@,48-57,/,.,-,_,+,,,$,:,~,{,}
 :endif
-:function! DeleteDirectory(dir)
-: if has("win16") || has("win32") || has("win64") || has("dos16") || has("dos32")
-:  exec "silent !rmdir /Q /S " . a:dir
-: else
-:  exec "silent !rm -rf " . a:dir
-: endif
-:endfun
+:"
 :if has("unix")
 :let $CDIR = "."
 /CDIR
@@ -45,7 +39,7 @@
 :" check for 'include' without \zs or \ze
 :lang C
 :call delete("./Xbase.a")
-:call DeleteDirectory("Xdir1")
+:call delete("Xdir1", "rf")
 :!mkdir Xdir1
 :!mkdir "Xdir1/dir2"
 :e! Xdir1/dir2/foo.a
@@ -70,7 +64,7 @@
 STARTTEST
 :" check for 'include' with \zs and \ze
 :call delete("./Xbase.b")
-:call DeleteDirectory("Xdir1")
+:call delete("Xdir1", "rf")
 :!mkdir Xdir1
 :!mkdir "Xdir1/dir2"
 :let &include='^\s*%inc\s*/\zs[^/]\+\ze'
@@ -100,7 +94,7 @@
 STARTTEST
 :" check for 'include' with \zs and no \ze
 :call delete("./Xbase.c")
-:call DeleteDirectory("Xdir1")
+:call delete("Xdir1", "rf")
 :!mkdir Xdir1
 :!mkdir "Xdir1/dir2"
 :let &include='^\s*%inc\s*\%([[:upper:]][^[:space:]]*\s\+\)\?\zs\S\+\ze'