diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 88efd19..dabf573 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -164,6 +164,7 @@
 # Keep test_alot*.res as the last one, sort the others.
 NEW_TESTS = test_arglist.res \
 	    test_assert.res \
+	    test_autochdir \
 	    test_backspace_opt.res \
 	    test_cdo.res \
 	    test_channel.res \
diff --git a/src/testdir/test_autochdir.vim b/src/testdir/test_autochdir.vim
new file mode 100644
index 0000000..f52e2e6
--- /dev/null
+++ b/src/testdir/test_autochdir.vim
@@ -0,0 +1,17 @@
+" Test 'autochdir' behavior
+
+if !exists("+autochdir")
+  finish
+endif
+
+func Test_set_filename()
+  call test_autochdir()
+  set acd
+  new
+  w samples/Xtest
+  call assert_equal("Xtest", expand('%'))
+  call assert_equal("samples", substitute(getcwd(), '.*/\(\k*\)', '\1', ''))
+  bwipe!
+  set noacd
+  call delete('samples/Xtest')
+endfunc