diff --git a/src/proto/memfile.pro b/src/proto/memfile.pro
index 3feb677..3983b47 100644
--- a/src/proto/memfile.pro
+++ b/src/proto/memfile.pro
@@ -9,6 +9,7 @@
 void mf_put __ARGS((memfile_T *mfp, bhdr_T *hp, int dirty, int infile));
 void mf_free __ARGS((memfile_T *mfp, bhdr_T *hp));
 int mf_sync __ARGS((memfile_T *mfp, int flags));
+void mf_set_dirty __ARGS((memfile_T *mfp));
 int mf_release_all __ARGS((void));
 blocknr_T mf_trans_del __ARGS((memfile_T *mfp, blocknr_T old_nr));
 void mf_set_ffname __ARGS((memfile_T *mfp));