diff --git a/drivers/kw2xrf/include/overwrites.h b/drivers/kw2xrf/include/overwrites.h
index 817ed8e095..c81426ce21 100644
--- a/drivers/kw2xrf/include/overwrites.h
+++ b/drivers/kw2xrf/include/overwrites.h
@@ -39,8 +39,8 @@ extern "C" {
 #endif
 
 typedef struct overwrites_tag {
-    char address;
-    char data;
+    uint8_t address;
+    uint8_t data;
 } overwrites_t;