diff --git a/src/gpio/gpio.c b/src/gpio/gpio.c
index 3c53940..96feaa1 100644
--- a/src/gpio/gpio.c
+++ b/src/gpio/gpio.c
@@ -44,7 +44,7 @@ static mraa_result_t
 mraa_gpio_get_valfp(mraa_gpio_context dev)
 {
     char bu[MAX_SIZE];
-    sprintf(bu, SYSFS_CLASS_GPIO "/gpio%d/value", dev->pin);
+    snprintf(bu, MAX_SIZE, SYSFS_CLASS_GPIO "/gpio%d/value", dev->pin);
     dev->value_fp = open(bu, O_RDWR);
     if (dev->value_fp == -1) {
         syslog(LOG_ERR, "gpio%i: Failed to open 'value': %s", dev->pin, strerror(errno));