diff --git a/lib/json/json.c b/lib/json/json.c
index 576e55f5623..2d9f01be002 100644
--- a/lib/json/json.c
+++ b/lib/json/json.c
@@ -903,6 +903,8 @@ static int measure_bytes(const char *bytes, size_t len, void *data)
 
 	*total += (ssize_t)len;
 
+	ARG_UNUSED(bytes);
+
 	return 0;
 }