diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
index e6abb1779a69..f905feff1b56 100644
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -5499,11 +5499,20 @@ sysctl_devices(SYSCTL_HANDLER_ARGS)
 	udev->dv_flags = dev->flags;
 	udev->dv_state = dev->state;
 	sbuf_new(&sb, udev->dv_fields, sizeof(udev->dv_fields), SBUF_FIXEDLEN);
-	sbuf_cat(&sb, dev->nameunit);
+	if (dev->nameunit != NULL)
+		sbuf_cat(&sb, dev->nameunit);
+	else
+		sbuf_putc(&sb, '\0');
 	sbuf_putc(&sb, '\0');
-	sbuf_cat(&sb, dev->desc);
+	if (dev->desc != NULL)
+		sbuf_cat(&sb, dev->desc);
+	else
+		sbuf_putc(&sb, '\0');
 	sbuf_putc(&sb, '\0');
-	sbuf_cat(&sb, dev->driver != NULL ? dev->driver->name : '\0');
+	if (dev->driver != NULL)
+		sbuf_cat(&sb, dev->driver->name);
+	else
+		sbuf_putc(&sb, '\0');
 	sbuf_putc(&sb, '\0');
 	bus_child_pnpinfo_sb(dev, &sb);
 	sbuf_putc(&sb, '\0');