diff --git a/mldsa/src/ct.h b/mldsa/src/ct.h
index f7953b3b0..2c38abc85 100644
--- a/mldsa/src/ct.h
+++ b/mldsa/src/ct.h
@@ -299,7 +299,7 @@ __contract__(
   ensures((return_value == 0) == forall(i, 0, len, (a[i] == b[i]))))
 {
   uint8_t r = 0, s = 0;
-  unsigned i;
+  size_t i;
 
   for (i = 0; i < len; i++)
   __loop__(