diff --git a/src/binn.c b/src/binn.c
index e75c46f..b556d08 100644
--- a/src/binn.c
+++ b/src/binn.c
@@ -1863,7 +1863,7 @@ void * APIENTRY binn_object_read_pair(const void *ptr, int pos, char *pkey, int
 /*** SEQUENTIAL READ FUNCTIONS *********************************************/
 /***************************************************************************/
 
-BOOL APIENTRY binn_iter_init(binn_iter *iter, void *ptr, int expected_type) {
+BOOL APIENTRY binn_iter_init(binn_iter *iter, const void *ptr, int expected_type) {
   int  type, count, size=0, header_size;
 
   ptr = binn_ptr(ptr);
diff --git a/src/binn.h b/src/binn.h
index 431c0ab..922d10e 100644
--- a/src/binn.h
+++ b/src/binn.h
@@ -497,7 +497,7 @@ typedef struct binn_iter_struct {
     int   current;
 } binn_iter;
 
-BOOL   APIENTRY binn_iter_init(binn_iter *iter, void *pbuf, int type);
+BOOL   APIENTRY binn_iter_init(binn_iter *iter, const void *pbuf, int type);
 
 // allocated
 binn * APIENTRY binn_list_next_value(binn_iter *iter);