diff --git a/src/proto/viminfo.pro b/src/proto/viminfo.pro
index a1f0337..b1f97f6 100644
--- a/src/proto/viminfo.pro
+++ b/src/proto/viminfo.pro
@@ -3,5 +3,6 @@
 void check_marks_read(void);
 int read_viminfo(char_u *file, int flags);
 void write_viminfo(char_u *file, int forceit);
+int buf_compare(const void *s1, const void *s2);
 void ex_viminfo(exarg_T *eap);
 /* vim: set ft=c : */