diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index bbd28be..c7dd41f 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -268,7 +268,7 @@
 
   " If using valgrind, make sure every run uses a different log file.
   if cmd =~ 'valgrind.*--log-file='
-    let cmd = substitute(cmd, '--log-file=\(^\s*\)', '--log-file=\1.' . g:valgrind_cnt, '')
+    let cmd = substitute(cmd, '--log-file=\(\S*\)', '--log-file=\1.' . g:valgrind_cnt, '')
     let g:valgrind_cnt += 1
   endif