diff --git a/src/testdir/test_clientserver.vim b/src/testdir/test_clientserver.vim
index 0f40371..811af13 100644
--- a/src/testdir/test_clientserver.vim
+++ b/src/testdir/test_clientserver.vim
@@ -35,7 +35,8 @@
   endif
 
   " Takes a short while for the server to be active.
-  call WaitFor('serverlist() =~ "' . name . '"')
+  " When using valgrind it takes much longer.
+  call WaitFor('serverlist() =~ "' . name . '"', 5000)
   call assert_match(name, serverlist())
 
   call remote_foreground(name)