diff --git a/Python/hamt.c b/Python/hamt.c
index c9acbbc..e54d3a4 100644
--- a/Python/hamt.c
+++ b/Python/hamt.c
@@ -729,7 +729,7 @@
         uint32_t key_idx = 2 * idx;
         uint32_t val_idx = key_idx + 1;
 
-        assert(val_idx < Py_SIZE(self));
+        assert(val_idx < (size_t)Py_SIZE(self));
 
         PyObject *key_or_null = self->b_array[key_idx];
         PyObject *val_or_node = self->b_array[val_idx];
@@ -1123,7 +1123,7 @@
     key_idx = idx * 2;
     val_idx = key_idx + 1;
 
-    assert(val_idx < Py_SIZE(self));
+    assert(val_idx < (size_t)Py_SIZE(self));
 
     key_or_null = self->b_array[key_idx];
     val_or_node = self->b_array[val_idx];