diff --git a/libraries/HID/HID.h b/libraries/HID/HID.h
index 1a87bb7..f4ca7ae 100644
--- a/libraries/HID/HID.h
+++ b/libraries/HID/HID.h
@@ -47,7 +47,7 @@
 class HIDDescriptorListNode {
 public:
   HIDDescriptorListNode *next = NULL;
-  HIDDescriptorListNode(const void *d, uint16_t l) : data(d), length(l) { }
+  HIDDescriptorListNode(const void *d, const uint16_t l) : data(d), length(l) { }
 
   const void* data;
   uint16_t length;