diff --git a/gio/tests/gdbus-connection.c b/gio/tests/gdbus-connection.c
index 51dd27f7e..0410a880a 100644
--- a/gio/tests/gdbus-connection.c
+++ b/gio/tests/gdbus-connection.c
@@ -86,7 +86,8 @@ static const GDBusInterfaceVTable boo_vtable =
 {
   NULL, /* _method_call */
   NULL, /* _get_property */
-  NULL  /* _set_property */
+  NULL,  /* _set_property */
+  { 0 }
 };
 
 /* Runs in a worker thread. */
diff --git a/gio/tests/gdbus-export.c b/gio/tests/gdbus-export.c
index 61d47e90a..aec21d7d0 100644
--- a/gio/tests/gdbus-export.c
+++ b/gio/tests/gdbus-export.c
@@ -127,6 +127,8 @@ static const GDBusInterfaceInfo foo2_interface_info =
   "org.example.Foo2",
   (GDBusMethodInfo **) &foo_method_info_pointers,
   (GDBusSignalInfo **) &foo_signal_info_pointers,
+  NULL,
+  NULL
 };
 
 static void
@@ -198,7 +200,8 @@ static const GDBusInterfaceVTable foo_vtable =
 {
   foo_method_call,
   foo_get_property,
-  foo_set_property
+  foo_set_property,
+  { 0 },
 };
 
 /* -------------------- */
@@ -311,7 +314,8 @@ static const GDBusInterfaceVTable dyna_interface_vtable =
 {
   dyna_cyber,
   NULL,
-  NULL
+  NULL,
+  { 0 }
 };
 
 /* ---------------------------------------------------------------------------------------------------- */
@@ -693,7 +697,8 @@ static const GDBusSubtreeVTable subtree_vtable =
 {
   subtree_enumerate,
   subtree_introspect,
-  subtree_dispatch
+  subtree_dispatch,
+  { 0 }
 };
 
 /* -------------------- */
@@ -747,7 +752,8 @@ static const GDBusSubtreeVTable dynamic_subtree_vtable =
 {
   dynamic_subtree_enumerate,
   dynamic_subtree_introspect,
-  dynamic_subtree_dispatch
+  dynamic_subtree_dispatch,
+  { 0 }
 };
 
 /* -------------------- */
@@ -1729,7 +1735,7 @@ test_async_properties (void)
   GError *error = NULL;
   guint registration_id, registration_id2;
   static const GDBusInterfaceVTable vtable = {
-    test_async_method_call, NULL, NULL
+    test_async_method_call, NULL, NULL, { 0 }
   };
 
   c = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
diff --git a/gio/tests/gdbus-test-codegen.c b/gio/tests/gdbus-test-codegen.c
index 36be37b72..0681e7ec8 100644
--- a/gio/tests/gdbus-test-codegen.c
+++ b/gio/tests/gdbus-test-codegen.c
@@ -1920,7 +1920,7 @@ check_object_manager (void)
   GError *error;
   GMainLoop *loop;
   OMData *om_data = NULL;
-  guint om_signal_id = -1;
+  guint om_signal_id = 0;
   GDBusObjectManager *pm = NULL;
   GList *object_proxies;
   GList *proxies;
@@ -2356,7 +2356,7 @@ check_object_manager (void)
   if (loop != NULL)
     g_main_loop_unref (loop);
 
-  if (om_signal_id != -1)
+  if (om_signal_id != 0)
     g_dbus_connection_signal_unsubscribe (c, om_signal_id);
   g_clear_object (&o3);
   g_clear_object (&o2);
diff --git a/gio/tests/socket.c b/gio/tests/socket.c
index ee098c55f..3a567ec9d 100644
--- a/gio/tests/socket.c
+++ b/gio/tests/socket.c
@@ -1694,7 +1694,8 @@ test_get_available (gconstpointer user_data)
 
       for (tries = 0; tries < 100; tries++)
         {
-          if (g_socket_get_available_bytes (server) > sizeof (data))
+          gssize res = g_socket_get_available_bytes (server);
+          if ((res == -1) || ((gsize) res > sizeof (data)))
             break;
           g_usleep (100000);
         }
diff --git a/gio/tests/testfilemonitor.c b/gio/tests/testfilemonitor.c
index 44c70805b..3a94a0353 100644
--- a/gio/tests/testfilemonitor.c
+++ b/gio/tests/testfilemonitor.c
@@ -120,7 +120,8 @@ check_expected_events (RecordedEvent *expected,
                        GList         *recorded,
                        Environment    env)
 {
-  gint i, li;
+  gsize i;
+  gint li;
   GList *l;
 
   for (i = 0, li = 0, l = recorded; i < n_expected && l != NULL;)
@@ -219,7 +220,7 @@ check_expected_events (RecordedEvent *expected,
               e2->event_type == G_FILE_MONITOR_EVENT_CHANGES_DONE_HINT)
             {
               g_test_message ("Event CHANGES_DONE_HINT ignored at "
-                              "expected index %d, recorded index %d", i, li);
+                              "expected index %"  G_GSIZE_FORMAT ", recorded index %d", i, li);
               li++, l = l->next;
               continue;
             }
@@ -227,7 +228,7 @@ check_expected_events (RecordedEvent *expected,
            * the event doesn't match, it means the expected event has lost. */
           else if (env & e1->optional)
             {
-              g_test_message ("Event %d at expected index %d skipped because "
+              g_test_message ("Event %d at expected index %" G_GSIZE_FORMAT " skipped because "
                               "it is marked as optional", e1->event_type, i);
               i++;
               continue;
diff --git a/glib/gstring.c b/glib/gstring.c
index 030d75316..caf338b3a 100644
--- a/glib/gstring.c
+++ b/glib/gstring.c
@@ -978,7 +978,7 @@ g_string_replace (GString     *string,
 {
   gsize f_len, r_len, pos;
   gchar *cur, *next;
-  gint n = 0;
+  guint n = 0;
 
   g_return_val_if_fail (string != NULL, 0);
   g_return_val_if_fail (find != NULL, 0);