diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index 47aeab3..dd2f012 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -301,7 +301,7 @@
   let cmd .= ' --not-a-term'
   let cmd .= ' --gui-dialog-file guidialogfile'
   " remove any environment variables
-  let cmd = substitute(cmd, '[A-Z_]*=\S\+ *', '', 'g')
+  let cmd = substitute(cmd, '[A-Z_]\+=\S\+ *', '', 'g')
 
   " If using valgrind, make sure every run uses a different log file.
   if cmd =~ 'valgrind.*--log-file='