diff --git a/morphisms/length_prefix.morphism-base b/morphisms/length_prefix.morphism-base
index a694931..c93dcbf 100644
--- a/morphisms/length_prefix.morphism-base
+++ b/morphisms/length_prefix.morphism-base
@@ -36,6 +36,6 @@ morph_array_as_lenpfx_to_continuation_bit (T:Type)
 
         dst[i] = src->items[i];
         if( i+1 < src->len )
-            dst[i] |= (1<<(n_bits-1));
+            dst[i] |= ((uint64_t)1<<(n_bits-1));
     }
 ```