diff --git a/src/structs.h b/src/structs.h
index 7a3e8d2..367c70d 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -123,6 +123,7 @@
 // alphabet coding.  To minimize changes to the code, I decided to just
 // increase the number of possible marks.
 #define NMARKS		('z' - 'a' + 1)	// max. # of named marks
+#define EXTRA_MARKS	10		// marks 0-9
 #define JUMPLISTSIZE	100		// max. # of marks in jump list
 #define TAGSTACKSIZE	20		// max. # of tags in tag stack