diff --git a/src/structs.h b/src/structs.h
index 6c8ef48..8da7c7b 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -645,6 +645,7 @@
 #define CMOD_KEEPPATTERNS   0x1000	// ":keeppatterns"
 #define CMOD_NOSWAPFILE	    0x2000	// ":noswapfile"
 #define CMOD_VIM9CMD	    0x4000	// ":vim9cmd"
+#define CMOD_LEGACY	    0x8000	// ":legacy"
 
     int		cmod_split;		// flags for win_split()
     int		cmod_tab;		// > 0 when ":tab" was used