diff --git a/nsock/src/gh_heap.c b/nsock/src/gh_heap.c
index 23413bc09..b40b7ed26 100644
--- a/nsock/src/gh_heap.c
+++ b/nsock/src/gh_heap.c
@@ -169,7 +169,7 @@ static int heap_grow(gh_heap_t *heap) {
   /* Do we really need to grow? */
   assert(heap->count == heap->highwm);
 
-  heap->slots = safe_realloc(heap->slots,
+  heap->slots = (gh_hnode_t **)safe_realloc(heap->slots,
                              (heap->count + GH_SLOTS) * sizeof(gh_hnode_t *));
   heap->highwm += GH_SLOTS;
   return 0;