diff --git a/mercurial/hgweb/server.py b/mercurial/hgweb/server.py
--- a/mercurial/hgweb/server.py
+++ b/mercurial/hgweb/server.py
@@ -197,7 +197,7 @@ def create_server(ui, repo):
 
     def openlog(opt, default):
         if opt and opt != '-':
-            return open(opt, 'w')
+            return open(opt, 'a')
         return default
 
     if repo is None:
diff --git a/tests/test-hgweb b/tests/test-hgweb
--- a/tests/test-hgweb
+++ b/tests/test-hgweb
@@ -7,7 +7,7 @@ mkdir da
 echo foo > da/foo
 echo foo > foo
 hg ci -Ambase -d '0 0'
-hg serve -p $HGPORT -d --pid-file=hg.pid
+hg serve -p $HGPORT -d --pid-file=hg.pid -A access.log
 cat hg.pid >> $DAEMON_PIDS
 echo % manifest
 ("$TESTDIR/get-with-headers.py" localhost:$HGPORT '/file/tip/?style=raw')
@@ -28,5 +28,12 @@ echo % should give a 400 - bad command
 echo % should give a 404 - file does not exist
 "$TESTDIR/get-with-headers.py" localhost:$HGPORT '/file/tip/bork?style=raw'
 
+echo % stop and restart
+kill `cat hg.pid`
+hg serve -p $HGPORT -d --pid-file=hg.pid -A access.log
+cat hg.pid >> $DAEMON_PIDS
+# Test the access/error files are opened in append mode
+python -c "print len(file('access.log').readlines()), 'log lines written'"
+
 echo % static file
 "$TESTDIR/get-with-headers.py" localhost:$HGPORT '/static/style-gitweb.css'
diff --git a/tests/test-hgweb.out b/tests/test-hgweb.out
--- a/tests/test-hgweb.out
+++ b/tests/test-hgweb.out
@@ -65,6 +65,8 @@ 404 Not Found
 
 
 error: Path not found: bork/
+% stop and restart
+7 log lines written
 % static file
 200 Script output follows