diff --git a/test/vtable/vtable_c.c b/test/vtable/vtable_c.c
index d01506b..105409f 100644
--- a/test/vtable/vtable_c.c
+++ b/test/vtable/vtable_c.c
@@ -1,16 +1,50 @@
 #include <systemd/sd-bus.h>
 
+#define UNUSED(x) (void)(x)
+
+int test_handler(sd_bus_message* m, void* userdata, sd_bus_error* ret_error)
+{
+    UNUSED(m);
+    UNUSED(userdata);
+    UNUSED(ret_error);
+    return 0;
+}
+int test_get(sd_bus* bus, const char* path, const char* interface,
+             const char* property, sd_bus_message* reply, void* userdata,
+             sd_bus_error* ret_error)
+{
+    UNUSED(bus);
+    UNUSED(path);
+    UNUSED(interface);
+    UNUSED(property);
+    UNUSED(reply);
+    UNUSED(userdata);
+    UNUSED(ret_error);
+    return 0;
+}
+int test_set(sd_bus* bus, const char* path, const char* interface,
+             const char* property, sd_bus_message* value, void* userdata,
+             sd_bus_error* ret_error)
+{
+    UNUSED(bus);
+    UNUSED(path);
+    UNUSED(interface);
+    UNUSED(property);
+    UNUSED(value);
+    UNUSED(userdata);
+    UNUSED(ret_error);
+    return 0;
+}
+
+typedef int (*sd_bus_message_handler_t)(sd_bus_message* m, void* userdata,
+                                        sd_bus_error* ret_error);
 const sd_bus_vtable example2[] = {
     SD_BUS_VTABLE_START(0),
-    SD_BUS_METHOD((const char*)1, (const char*)2, (const char*)3,
-                  (sd_bus_message_handler_t)4, 0),
-    SD_BUS_SIGNAL((const char*)5, (const char*)6, 0),
-    SD_BUS_PROPERTY((const char*)7, (const char*)8, (sd_bus_property_get_t)9, 0,
-                    SD_BUS_VTABLE_PROPERTY_CONST),
-    SD_BUS_WRITABLE_PROPERTY((const char*)10, (const char*)11,
-                             (sd_bus_property_get_t)12,
-                             (sd_bus_property_set_t)13, 0, 0),
-    SD_BUS_PROPERTY((const char*)14, (const char*)15, NULL, 16, 0),
+    SD_BUS_METHOD("1", "2", "3", &test_handler, 0),
+    SD_BUS_SIGNAL("5", "6", 0),
+    SD_BUS_PROPERTY("7", "8", &test_get, 0, SD_BUS_VTABLE_PROPERTY_CONST),
+    SD_BUS_WRITABLE_PROPERTY("10", "11", &test_get, &test_set, 0, 0),
+    SD_BUS_PROPERTY("14", "15", NULL, 16, 0),
     SD_BUS_VTABLE_END,
 };