diff --git a/src/arena.c b/src/arena.c
index 790b6ac1..09afd890 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -482,7 +482,7 @@ static void mi_arena_schedule_purge(mi_arena_t* arena, size_t bitmap_idx, size_t
     // schedule decommit
     mi_msecs_t expire = mi_atomic_loadi64_relaxed(&arena->purge_expire);
     if (expire != 0) {
-      mi_atomic_addi64_acq_rel(&arena->purge_expire, delay/10);  // add smallish extra delay
+      mi_atomic_addi64_acq_rel(&arena->purge_expire, (mi_msecs_t)(delay/10));  // add smallish extra delay
     }
     else {
       mi_atomic_storei64_release(&arena->purge_expire, _mi_clock_now() + delay);
@@ -526,7 +526,7 @@ static bool mi_arena_try_purge(mi_arena_t* arena, mi_msecs_t now, bool force, mi
   if (!force && expire > now) return false;
 
   // reset expire (if not already set concurrently)
-  mi_atomic_casi64_strong_acq_rel(&arena->purge_expire, &expire, 0);
+  mi_atomic_casi64_strong_acq_rel(&arena->purge_expire, &expire, (mi_msecs_t)0);
 
   // potential purges scheduled, walk through the bitmap
   bool any_purged = false;