diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 218567f..eeeb4e3 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -466,3 +466,8 @@
 
   set fileformats&
 endfunc
+
+func Test_balloon_show()
+  " This won't do anything but must not crash either.
+  call balloon_show('hi!')
+endfunc