diff --git a/glib/gmain.c b/glib/gmain.c
index c651e9147..b9b25f1e6 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -574,6 +574,8 @@ retry_decrement:
     }
   g_source_iter_clear (&iter);
 
+  g_rw_lock_writer_unlock (&source_destroy_lock);
+
   /* Next destroy all sources. As we still hold a reference to all of them,
    * this won't cause any of them to be freed yet and especially prevents any
    * source that unrefs another source from its finalize function to be freed.
@@ -584,8 +586,6 @@ retry_decrement:
       g_source_destroy_internal (source, context, TRUE);
     }
 
-  g_rw_lock_writer_unlock (&source_destroy_lock);
-
   /* the context is going to die now */
   g_return_if_fail (old_ref > 0);
 
diff --git a/glib/tests/mainloop.c b/glib/tests/mainloop.c
index 243becdee..b1a21293f 100644
--- a/glib/tests/mainloop.c
+++ b/glib/tests/mainloop.c
@@ -2384,6 +2384,38 @@ test_maincontext_source_finalization_from_dispatch (gconstpointer user_data)
   g_main_context_unref (c);
 }
 
+static void
+callback_source_unref (gpointer cb_data)
+{
+  GSource *s = (GSource *) cb_data;
+
+  g_source_destroy (s);
+};
+
+static GSourceCallbackFuncs callback_funcs = {
+  NULL,
+  callback_source_unref,
+  NULL,
+};
+
+static void
+test_context_ref_while_in_source_callbackfuncs_unref (void)
+{
+  GMainContext *c = g_main_context_new ();
+  GSource *s;
+
+  g_test_summary ("Tests if calling GSource API in GSourceCallbackFuncs.unref "
+                  "does not deadlock attempting to retrieve the relevant GMainContext.");
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/issues/3725");
+
+  s = g_source_new (&source_with_source_funcs, sizeof (SourceWithSource));
+  g_source_set_callback_indirect (s, s, &callback_funcs);
+  g_source_attach (s, c);
+  g_source_unref (s);
+
+  g_main_context_unref (c);
+}
+
 static void
 once_cb (gpointer user_data)
 {
@@ -2671,6 +2703,7 @@ main (int argc, char *argv[])
     }
   g_test_add_func ("/maincontext/idle-once", test_maincontext_idle_once);
   g_test_add_func ("/maincontext/timeout-once", test_maincontext_timeout_once);
+  g_test_add_func ("/maincontext/context-ref-in-source-callbackfuncs-unref", test_context_ref_while_in_source_callbackfuncs_unref);
 
   g_test_add_func ("/mainloop/basic", test_mainloop_basic);
   g_test_add_func ("/mainloop/timeouts", test_timeouts);