diff -r 9d0505d80044 -r 7eea57f6d847 dav/main.c
--- a/dav/main.c	Sun Sep 24 11:31:01 2017 +0200
+++ b/dav/main.c	Sun Sep 24 14:31:42 2017 +0200
@@ -1175,6 +1175,10 @@
         propname.name = property;
     } else {
         dav_get_property_namespace_str(ctx, property, &propname.ns, &propname.name);
+        if(!propname.ns || !propname.name) {
+            fprintf(stderr, "Error: unknown namespace prefix\n");
+            return -1;
+        }
     }
     
     DavResource *res = dav_resource_new(sn, path);