diff --git a/extmod/moductypes.c b/extmod/moductypes.c
index 0f28a34688..73a8db7cc0 100644
--- a/extmod/moductypes.c
+++ b/extmod/moductypes.c
@@ -261,10 +261,10 @@ STATIC inline mp_obj_t get_unaligned(uint val_type, void *p, int big_endian) {
     }
 }
 
-STATIC inline void set_unaligned(uint val_type, void *p, int big_endian, mp_obj_t val) {
+STATIC inline void set_unaligned(uint val_type, byte *p, int big_endian, mp_obj_t val) {
     char struct_type = big_endian ? '>' : '<';
     static const char type2char[8] = "BbHhIiQq";
-    mp_binary_set_val(struct_type, type2char[val_type], val, (byte**)&p);
+    mp_binary_set_val(struct_type, type2char[val_type], val, &p);
 }
 
 static inline mp_uint_t get_aligned_basic(uint val_type, void *p) {