diff --git a/src/emu/ovnisort.c b/src/emu/ovnisort.c
index 86c07d1..e7c0b47 100644
--- a/src/emu/ovnisort.c
+++ b/src/emu/ovnisort.c
@@ -49,7 +49,7 @@ enum operation_mode { SORT,
 
 static char *tracedir = NULL;
 static enum operation_mode operation_mode = SORT;
-static const size_t max_look_back = 1000000;
+static size_t max_look_back = 1000000;
 
 static void
 ring_reset(struct ring *r)
@@ -404,6 +404,9 @@ usage(void)
 	rerr("  -c          Enable check mode: don't sort, ensure the\n");
 	rerr("              trace is already sorted.\n");
 	rerr("\n");
+	rerr("  -n          Set the number of events to look back.\n");
+	rerr("              Defaul: %ld\n", max_look_back);
+	rerr("\n");
 	rerr("  tracedir    The trace directory generated by ovni.\n");
 	rerr("\n");
 
@@ -415,11 +418,14 @@ parse_args(int argc, char *argv[])
 {
 	int opt;
 
-	while ((opt = getopt(argc, argv, "c")) != -1) {
+	while ((opt = getopt(argc, argv, "cn:")) != -1) {
 		switch (opt) {
 			case 'c':
 				operation_mode = CHECK;
 				break;
+			case 'n':
+				max_look_back = atol(optarg);
+				break;
 			default: /* '?' */
 				usage();
 		}