diff --git a/include/nuttx/ioexpander/gpio.h b/include/nuttx/ioexpander/gpio.h
index 6436a2d13f6..6cd73816068 100644
--- a/include/nuttx/ioexpander/gpio.h
+++ b/include/nuttx/ioexpander/gpio.h
@@ -120,7 +120,7 @@ struct gpio_dev_s
 
   FAR const struct gpio_operations_s *gp_ops;
 
-  /* Device specific information may follow */
+  /* Device specific, lower-half information may follow */
 };
 
 /****************************************************************************