diff --git a/cmd-set-option.c b/cmd-set-option.c
index 83d31b93..77c7d7c2 100644
--- a/cmd-set-option.c
+++ b/cmd-set-option.c
@@ -266,16 +266,25 @@ cmd_set_option_unset(struct cmd *self, struct cmd_q *cmdq,
 {
 	struct args	*args = self->args;
 
-	if (args_has(args, 'g')) {
-		cmdq_error(cmdq, "can't unset global option: %s", oe->name);
-		return (-1);
-	}
 	if (value != NULL) {
 		cmdq_error(cmdq, "value passed to unset option: %s", oe->name);
 		return (-1);
 	}
 
-	options_remove(oo, oe->name);
+	if (args_has(args, 'g') || oo == &global_options) {
+		switch (oe->type) {
+		case OPTIONS_TABLE_STRING:
+			options_set_string(oo, oe->name, "%s", oe->default_str);
+			break;
+		case OPTIONS_TABLE_STYLE:
+			options_set_style(oo, oe->name, oe->default_str, 0);
+			break;
+		default:
+			options_set_number(oo, oe->name, oe->default_num);
+			break;
+		}
+	} else
+		options_remove(oo, oe->name);
 	return (0);
 }
 
diff --git a/tmux.1 b/tmux.1
index 11fe6b7e..125a13f2 100644
--- a/tmux.1
+++ b/tmux.1
@@ -2277,21 +2277,19 @@ command),
 a server option with
 .Fl s ,
 otherwise a session option.
-.Pp
 If
 .Fl g
-is specified, the global session or window option is set.
+is given, the global session or window option is set.
 The
 .Fl u
 flag unsets an option, so a session inherits the option from the global
-options.
-It is not possible to unset a global option.
+options (or with
+.Fl g ,
+restores a global option to the default).
 .Pp
 The
 .Fl o
-flag prevents setting an option that is already set.
-.Pp
-The
+flag prevents setting an option that is already set and
 .Fl q
 flag suppresses errors about unknown options.
 .Pp