diff --git a/drivers/gpio/gpio_pcal9535a.c b/drivers/gpio/gpio_pcal9535a.c
index ba7a30ab493..e3fef26986a 100644
--- a/drivers/gpio/gpio_pcal9535a.c
+++ b/drivers/gpio/gpio_pcal9535a.c
@@ -542,7 +542,7 @@ static const struct gpio_driver_api gpio_pcal9535a_drv_api_funcs = {
  * @param dev Device struct
  * @return 0 if successful, failed otherwise.
  */
-int gpio_pcal9535a_init(struct device *dev)
+static int gpio_pcal9535a_init(struct device *dev)
 {
 	const struct gpio_pcal9535a_config * const config =
 		dev->config->config_info;
diff --git a/drivers/gpio/gpio_pcal9535a.h b/drivers/gpio/gpio_pcal9535a.h
index c1c0b2da7a6..59e08ad5d94 100644
--- a/drivers/gpio/gpio_pcal9535a.h
+++ b/drivers/gpio/gpio_pcal9535a.h
@@ -30,14 +30,6 @@
 extern "C" {
 #endif
 
-/**
- * @brief Initialization function for PCAL9535A
- *
- * @param dev Device struct
- * @return 0 if successful, failed otherwise
- */
-extern int gpio_pcal9535a_init(struct device *dev);
-
 /** Configuration data */
 struct gpio_pcal9535a_config {
 	/** The master I2C device's name */