diff --git a/include/picrin.h b/include/picrin.h
index c69b2d46..ba688f02 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -86,7 +86,7 @@ enum pic_parser_res {
 
 void *pic_alloc(pic_state *, size_t);
 void *pic_realloc(pic_state *, void *, size_t);
-void *pic_calloc(pic_state *, unsigned, size_t);
+void *pic_calloc(pic_state *, size_t, size_t);
 struct pic_object *pic_obj_alloc(pic_state *, size_t, enum pic_tt);
 struct pic_object *pic_obj_alloc_unsafe(pic_state *, size_t, enum pic_tt);
 void pic_free(pic_state *, void *);
diff --git a/src/gc.c b/src/gc.c
index 1ddd6f43..faab9e70 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -61,7 +61,7 @@ pic_realloc(pic_state *pic, void *ptr, size_t size)
 }
 
 void *
-pic_calloc(pic_state *pic, unsigned count, size_t size)
+pic_calloc(pic_state *pic, size_t count, size_t size)
 {
   void *ptr;