diff --git a/drivers/ioexpander/gpio.c b/drivers/ioexpander/gpio.c
index 2d5ffa9b35f..d7f1e966fa9 100644
--- a/drivers/ioexpander/gpio.c
+++ b/drivers/ioexpander/gpio.c
@@ -183,7 +183,7 @@ static int gpio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
    */
 
   case GPIO_WRITE:
-    if (dev->output)
+    if (dev->gp_output)
       {
         FAR struct gpio_output_dev_s *outdev =
           (FAR struct gpio_output_dev_s *)dev;
@@ -204,7 +204,7 @@ static int gpio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
    */
 
   case GPIO_READ:
-    if (dev->output)
+    if (dev->gp_output)
       {
         FAR struct gpio_output_dev_s *outdev =
           (FAR struct gpio_output_dev_s *)dev;
@@ -242,7 +242,7 @@ int gpio_input_register(FAR struct gpio_input_dev_s *dev, int minor)
 {
   char devname[16];
 
-  DEBUGASSERT((unsigned int)minor < 100);
+  DEBUGASSERT(dev != NULL && !dev->output && (unsigned int)minor < 100);
   snprintf(devname, 16, "/dev/gpin%u", (unsigned int)minor);
 
   return register_driver(devname, &g_gpio_input_ops, 0444, dev);
@@ -260,7 +260,7 @@ int gpio_output_register(FAR struct gpio_output_dev_s *dev, int minor)
 {
   char devname[16];
 
-  DEBUGASSERT((unsigned int)minor < 100);
+  DEBUGASSERT(dev != NULL && dev->output && (unsigned int)minor < 100);
   snprintf(devname, 16, "/dev/gpout%u", (unsigned int)minor);
 
   return register_driver(devname, &g_gpio_output_ops, 0222, dev);
diff --git a/include/nuttx/ioexpander/gpio.h b/include/nuttx/ioexpander/gpio.h
index 5d6e7917467..1e5ae50cc73 100644
--- a/include/nuttx/ioexpander/gpio.h
+++ b/include/nuttx/ioexpander/gpio.h
@@ -70,16 +70,16 @@
 
 struct gpio_common_dev_s
 {
-  bool output;
-  uint8_t unused[3];
+  bool gp_output;
+  uint8_t gp_unused[3];
 };
 
 /* The interface to a GPIO input pin */
 
 struct gpio_input_dev_s
 {
-  bool output;
-  uint8_t unused[3];
+  bool gpin_output;
+  uint8_t gpin_unused[3];
   CODE int (*gpin_read)(FAR struct gpio_input_dev_s *dev);
 };
 
@@ -87,8 +87,8 @@ struct gpio_input_dev_s
 
 struct gpio_output_dev_s
 {
-  bool output;
-  uint8_t unused[3];
+  bool gpout_output;
+  uint8_t gpout_unused[3];
   CODE int (*gpout_read)(FAR struct gpio_output_dev_s *dev);
   CODE int (*gpout_write)(FAR struct gpio_output_dev_s *dev, int value);
 };