diff --git a/allchblk.c b/allchblk.c
index a7af5cfdd..cee985b82 100644
--- a/allchblk.c
+++ b/allchblk.c
@@ -796,7 +796,7 @@ static struct hblk *find_nonbl_hblk(struct hblk *last_hbp, word size_remain,
 static void drop_hblk_in_chunks(int n, struct hblk *hbp, hdr *hhdr)
 {
   size_t total_size = (size_t)(hhdr -> hb_sz);
-  struct hblk *limit = hbp + divHBLKSZ(total_size);
+  const struct hblk *limit = hbp + divHBLKSZ(total_size);
 
   GC_ASSERT(HDR(hbp) == hhdr);
   GC_ASSERT(modHBLKSZ(total_size) == 0 && total_size > 0);
diff --git a/mark.c b/mark.c
index 770b611a8..440dfa2eb 100644
--- a/mark.c
+++ b/mark.c
@@ -763,7 +763,7 @@ GC_INNER mse * GC_mark_from(mse *mark_stack_top, mse *mark_stack,
           mark_stack_top--;
 #         ifdef ENABLE_TRACE
             if (ADDR_GE(GC_trace_addr, current_p)) {
-              void *base = GC_base(current_p);
+              const void *base = GC_base(current_p);
 
               if (base != NULL && GC_base(GC_trace_addr) == base) {
                 GC_log_printf("GC #%lu: tracing from %p, proc descr %lu\n",