diff --git a/julia.c b/julia.c
index bdecdfa..253609f 100644
--- a/julia.c
+++ b/julia.c
@@ -128,7 +128,7 @@ usage(void)
 	fprintf(stderr, "Usage: %s julia [-L] [-x julia_x] [-y julia_y]\n"
 	    "    [-n niters] [-h height] [-w width] [-z zoom]\n"
 	    "    [-a center_x] [-b center_y] [-l light_intensity]\n"
-	    "    [-d density] [-c contour]\n",
+	    "    [-d density] [-c contour] [-D displacement]\n",
 	    xgetprogname());
 	exit(1);
 }
@@ -161,7 +161,7 @@ julia_main(int argc, char *argv[])
 	    i, j;
 	int ch, do_light = 0;
 
-	while ((ch = getopt(argc, argv, "a:b:c:d:h:Ll:n:w:x:y:z:")) != -1)
+	while ((ch = getopt(argc, argv, "a:b:c:D:d:h:Ll:n:w:x:y:z:")) != -1)
 		switch (ch) {
 		case 'a':
 			errno = 0;
@@ -191,6 +191,15 @@ julia_main(int argc, char *argv[])
 				exit(1);
 			}
 			break;
+		case 'D':
+			errno = 0;
+			displacement = strtold(optarg, &end);
+			if (end == optarg || *end != '\0' || errno != 0) {
+				fprintf(stderr, "-d: invalid value \"%s\"",
+				    optarg);
+				exit(1);
+			}
+			break;
 		case 'd':
 			errno = 0;
 			density = strtold(optarg, &end);