diff -up PackageKit-0.7.2/lib/packagekit-glib2/pk-control.c.null PackageKit-0.7.2/lib/packagekit-glib2/pk-control.c
--- PackageKit-0.7.2/lib/packagekit-glib2/pk-control.c.null	2012-01-20 00:02:52.422053263 -0500
+++ PackageKit-0.7.2/lib/packagekit-glib2/pk-control.c	2012-01-20 00:04:04.368050690 -0500
@@ -1175,12 +1175,12 @@ pk_control_set_proxy2_async (PkControl *
 	state->res = g_object_ref (res);
 	state->control = g_object_ref (control);
 	state->parameters = g_variant_new ("(ssssss)",
-					   proxy_http,
-					   proxy_https,
-					   proxy_ftp,
-					   proxy_socks,
-					   no_proxy,
-					   pac);
+					   proxy_http ? proxy_http : "",
+					   proxy_https ? proxy_https : "",
+					   proxy_ftp ? proxy_ftp : "",
+					   proxy_socks ? proxy_socks : "",
+					   no_proxy ? no_proxy : "",
+					   pac ? pac : "");
 	if (cancellable != NULL)
 		state->cancellable = g_object_ref (cancellable);