diff --git a/src/bool.c b/src/bool.c
index 07ddcffc..bb4fae82 100644
--- a/src/bool.c
+++ b/src/bool.c
@@ -25,7 +25,7 @@ pic_equal_p(pic_state *pic, pic_value x, pic_value y)
   case PIC_TT_PAIR:
     return pic_equal_p(pic, pic_car(pic, x), pic_car(pic, y)) && pic_equal_p(pic, pic_cdr(pic, x), pic_cdr(pic, y));
   case PIC_TT_BLOB: {
-    int i;
+    size_t i;
     struct pic_blob *u = pic_blob_ptr(x), *v = pic_blob_ptr(y);
 
     if(u->len != v->len){