diff --git a/fs/jffs2/jffs2_private.h b/fs/jffs2/jffs2_private.h
index 658b325..06b6ca2 100644
--- a/fs/jffs2/jffs2_private.h
+++ b/fs/jffs2/jffs2_private.h
@@ -98,4 +98,8 @@
 	}
 }
 
+#if defined(CONFIG_SYS_JFFS2_SORT_FRAGMENTS)
+/* External merge sort. */
+int sort_list(struct b_list *list);
+#endif
 #endif /* jffs2_private.h */