diff --git a/src/testdir/test_termcodes.vim b/src/testdir/test_termcodes.vim
index ec02086..055ed8b 100644
--- a/src/testdir/test_termcodes.vim
+++ b/src/testdir/test_termcodes.vim
@@ -851,7 +851,10 @@
   let save_term = &term
   let save_ttymouse = &ttymouse
   call test_override('no_query_mouse', 1)
-  set mouse=a term=xterm mousetime=200
+  
+  " 'mousetime' must be sufficiently large, or else the test is flaky when
+  " using a ssh connection with X forwarding; i.e. ssh -X (issue #7563).
+  set mouse=a term=xterm mousetime=600
   new
 
   for ttymouse_val in g:Ttymouse_values + g:Ttymouse_dec