diff --git a/tools/gpio/gpio-utils.h b/tools/gpio/gpio-utils.h
index b18209a..5f57133 100644
--- a/tools/gpio/gpio-utils.h
+++ b/tools/gpio/gpio-utils.h
@@ -16,6 +16,8 @@
 
 #include <string.h>
 
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+
 static inline int check_prefix(const char *str, const char *prefix)
 {
 	return strlen(str) > strlen(prefix) &&