diff --git a/src/sage/combinat/designs/subhypergraph_search.pyx b/src/sage/combinat/designs/subhypergraph_search.pyx
index 267ff3b2fe0..c31e8dcd229 100644
--- a/src/sage/combinat/designs/subhypergraph_search.pyx
+++ b/src/sage/combinat/designs/subhypergraph_search.pyx
@@ -295,7 +295,7 @@ cdef int is_subhypergraph_admissible(hypergraph h1,hypergraph * h2_trace,int n,h
 
     return 1
 
-cdef int cmp_128_bits(void * a, void * b) noexcept nogil:
+cdef int cmp_128_bits(const void * a, const void * b) noexcept nogil:
     r"""
     Lexicographic order on 128-bits words
     """