diff --git a/runtime/gc/heap.h b/runtime/gc/heap.h
index e11671b..e568b36 100644
--- a/runtime/gc/heap.h
+++ b/runtime/gc/heap.h
@@ -408,7 +408,7 @@
 
   // Implements java.lang.Runtime.freeMemory.
   size_t GetFreeMemory() const {
-    return GetTotalMemory() - num_bytes_allocated_.LoadSequentiallyConsistent();
+    return GetMaxMemory() - num_bytes_allocated_.LoadSequentiallyConsistent();
   }
 
   // get the space that corresponds to an object's address. Current implementation searches all