diff --git a/sbin/geom/class/part/geom_part.c b/sbin/geom/class/part/geom_part.c
index 673d90cd1619..972e2ffaaf53 100644
--- a/sbin/geom/class/part/geom_part.c
+++ b/sbin/geom/class/part/geom_part.c
@@ -90,16 +90,16 @@ struct g_command PUBSYM(class_commands)[] = {
 		{ 'b', "start", GPART_AUTOFILL, G_TYPE_STRING },
 		{ 's', "size", GPART_AUTOFILL, G_TYPE_STRING },
 		{ 't', "type", NULL, G_TYPE_STRING },
-		{ 'i', GPART_PARAM_INDEX, "", G_TYPE_ASCNUM },
-		{ 'l', "label", "", G_TYPE_STRING },
+		{ 'i', GPART_PARAM_INDEX, G_VAL_OPTIONAL, G_TYPE_ASCNUM },
+		{ 'l', "label", G_VAL_OPTIONAL, G_TYPE_STRING },
 		{ 'f', "flags", GPART_FLAGS, G_TYPE_STRING },
 		G_OPT_SENTINEL },
 	    "[-b start] [-s size] -t type [-i index] [-l label] [-f flags] geom"
 	},
 	{ "bootcode", 0, gpart_bootcode, {
-		{ 'b', GPART_PARAM_BOOTCODE, "", G_TYPE_STRING },
-		{ 'p', GPART_PARAM_PARTCODE, "", G_TYPE_STRING },
-		{ 'i', GPART_PARAM_INDEX, "", G_TYPE_ASCNUM },
+		{ 'b', GPART_PARAM_BOOTCODE, G_VAL_OPTIONAL, G_TYPE_STRING },
+		{ 'p', GPART_PARAM_PARTCODE, G_VAL_OPTIONAL, G_TYPE_STRING },
+		{ 'i', GPART_PARAM_INDEX, G_VAL_OPTIONAL, G_TYPE_ASCNUM },
 		{ 'f', "flags", GPART_FLAGS, G_TYPE_STRING },
 		G_OPT_SENTINEL },
 	    "bootcode [-b bootcode] [-p partcode] [-i index] [-f flags] geom"
@@ -109,7 +109,7 @@ struct g_command PUBSYM(class_commands)[] = {
 	},
 	{ "create", 0, gpart_issue, {
 		{ 's', "scheme", NULL, G_TYPE_STRING },
-		{ 'n', "entries", "", G_TYPE_ASCNUM },
+		{ 'n', "entries", G_VAL_OPTIONAL, G_TYPE_ASCNUM },
 		{ 'f', "flags", GPART_FLAGS, G_TYPE_STRING },
 		G_OPT_SENTINEL },
 	    "-s scheme [-n entries] [-f flags] provider"
@@ -127,8 +127,8 @@ struct g_command PUBSYM(class_commands)[] = {
 	},
 	{ "modify", 0, gpart_issue, {
 		{ 'i', GPART_PARAM_INDEX, NULL, G_TYPE_ASCNUM },
-		{ 'l', "label", "", G_TYPE_STRING },
-		{ 't', "type", "", G_TYPE_STRING },
+		{ 'l', "label", G_VAL_OPTIONAL, G_TYPE_STRING },
+		{ 't', "type", G_VAL_OPTIONAL, G_TYPE_STRING },
 		{ 'f', "flags", GPART_FLAGS, G_TYPE_STRING },
 		G_OPT_SENTINEL },
 	    "-i index [-l label] [-t type] [-f flags] geom"
diff --git a/sbin/geom/core/geom.c b/sbin/geom/core/geom.c
index 39731e964a34..d83a232e6785 100644
--- a/sbin/geom/core/geom.c
+++ b/sbin/geom/core/geom.c
@@ -374,9 +374,8 @@ parse_arguments(struct g_command *cmd, struct gctl_req *req, int *argc,
 				warnx("Option '%c' not specified.",
 				    opt->go_char);
 				usage();
-			} else if (G_OPT_TYPE(opt) == G_TYPE_ASCNUM &&
-			    *(const char *)opt->go_val == '\0') {
-			    	;	/* add nothing. */
+			} else if (opt->go_val == G_VAL_OPTIONAL) {
+				/* add nothing. */
 			} else {
 				set_option(req, opt, opt->go_val);
 			}
diff --git a/sbin/geom/core/geom.h b/sbin/geom/core/geom.h
index c88005ef10ad..a148ddaac7ad 100644
--- a/sbin/geom/core/geom.h
+++ b/sbin/geom/core/geom.h
@@ -53,6 +53,8 @@
 #define	G_OPT_NUM(opt)		(((opt)->go_type & G_TYPE_NUMMASK) >> G_TYPE_NUMSHIFT)
 #define	G_OPT_NUMINC(opt)	((opt)->go_type += (1 << G_TYPE_NUMSHIFT))
 
+#define	G_VAL_OPTIONAL	((void *)-1)
+
 #define G_OPT_SENTINEL	{ '\0', NULL, NULL, G_TYPE_NONE }
 #define G_NULL_OPTS	{ G_OPT_SENTINEL }
 #define	G_CMD_SENTINEL	{ NULL, 0, NULL, G_NULL_OPTS, NULL }