--- a/hgext/journal.py	Sun Aug 07 17:15:19 2016 +0200
+++ b/hgext/journal.py	Mon Aug 08 18:05:10 2016 +0200
@@ -165,9 +165,10 @@
 
 def wrappostshare(orig, sourcerepo, destrepo, **kwargs):
     """Mark this shared working copy as sharing journal information"""
-    orig(sourcerepo, destrepo, **kwargs)
-    with destrepo.vfs('shared', 'a') as fp:
-        fp.write('journal\n')
+    with destrepo.wlock():
+        orig(sourcerepo, destrepo, **kwargs)
+        with destrepo.vfs('shared', 'a') as fp:
+            fp.write('journal\n')
 
 def unsharejournal(orig, ui, repo, repopath):
     """Copy shared journal entries into this repo when unsharing"""