diff -rubB modules/dav/acl/mod_dav_acl.c modules/dav/acl/mod_dav_acl.c
--- modules/dav/acl/mod_dav_acl.c	2009-09-07 16:16:10.000000000 -0400
+++ modules/dav/acl/mod_dav_acl.c	2009-09-07 20:36:46.000000000 -0400
@@ -66,6 +66,24 @@
     NULL
 };
 
+/** resource type hooks for principals */
+int acl_get_resource_type(const dav_resource *resource, 
+			  const char **name, 
+			  const char **uri)
+{
+    if (resource->exists && !resource->collection) {
+	*name = "principal";
+	*uri = "DAV:";
+	return 0;
+    }
+
+    return -1;
+}
+
+static dav_resource_type_provider res_type = {
+    acl_get_resource_type, 
+};
+
 static const command_rec dav_acl_cmds[] = {
     { NULL }
 };
@@ -73,6 +92,7 @@
 static void register_hooks(apr_pool_t *p)
 {
     dav_options_provider_register (p, "acl", &options);
+    dav_resource_type_provider_register (p, "acl", &res_type);
 }
 
 module AP_MODULE_DECLARE_DATA dav_acl_module = {