diff --git a/src/mini_heap.h b/src/mini_heap.h
index a480b22..9d1639a 100644
--- a/src/mini_heap.h
+++ b/src/mini_heap.h
@@ -281,7 +281,7 @@ class MiniHeap {
   }
 
   inline size_t bytesFree() const {
-    return inUseCount() * objectSize();
+    return (maxCount() - inUseCount()) * objectSize();
   }
 
   inline void setMeshed() {