diff --git a/src/option.h b/src/option.h
index d5f72a1..18a7c2a 100644
--- a/src/option.h
+++ b/src/option.h
@@ -794,6 +794,7 @@
 #endif
 EXTERN long	p_mouset;	// 'mousetime'
 EXTERN int	p_more;		// 'more'
+EXTERN long	p_mhi;		// 'msghistory'
 #ifdef FEAT_MZSCHEME
 EXTERN long	p_mzq;		// 'mzquantum
 # if defined(DYNAMIC_MZSCHEME)