diff --git a/glib/gmain.c b/glib/gmain.c
index af0a29ae5..7a5ec1f45 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -2112,11 +2112,15 @@ g_source_unref_internal (GSource      *source,
 
       if (source->source_funcs->finalize)
 	{
+          /* Temporarily increase the ref count again so that GSource methods
+           * can be called from finalize(). */
+          source->ref_count++;
 	  if (context)
 	    UNLOCK_CONTEXT (context);
 	  source->source_funcs->finalize (source);
 	  if (context)
 	    LOCK_CONTEXT (context);
+          source->ref_count--;
 	}
 
       g_free (source->name);
diff --git a/glib/gmain.h b/glib/gmain.h
index e8cdeed7a..26400d44b 100644
--- a/glib/gmain.h
+++ b/glib/gmain.h
@@ -104,7 +104,10 @@ typedef struct _GSourceCallbackFuncs    GSourceCallbackFuncs;
  *     are needed for this type of event source. The return value of the
  *     @dispatch function should be #G_SOURCE_REMOVE if the source should be
  *     removed or #G_SOURCE_CONTINUE to keep it.
- * @finalize: Called when the source is finalized.
+ * @finalize: Called when the source is finalized. At this point, the source
+ *     will have been destroyed, had its callback cleared, and have been removed
+ *     from its #GMainContext, but it will still have its final reference count;
+ *     so methods can be called on it from within this function.
  *
  * The `GSourceFuncs` struct contains a table of
  * functions used to handle event sources in a generic manner.