diff --git a/src/proto/option.pro b/src/proto/option.pro
index d0ba4ec..3da0e94 100644
--- a/src/proto/option.pro
+++ b/src/proto/option.pro
@@ -63,4 +63,5 @@
 long get_sts_value(void);
 void find_mps_values(int *initc, int *findc, int *backwards, int switchit);
 unsigned int get_bkc_value(buf_T *buf);
+int signcolumn_on(win_T *wp);
 /* vim: set ft=c : */