diff --git a/runtime/java_vm_ext.h b/runtime/java_vm_ext.h
index 8c81c25..ac20afe 100644
--- a/runtime/java_vm_ext.h
+++ b/runtime/java_vm_ext.h
@@ -225,7 +225,7 @@
 
   // Extra checking.
   bool check_jni_;
-  bool force_copy_;
+  const bool force_copy_;
   const bool tracing_enabled_;
 
   // Extra diagnostics.