diff --git a/src/editor/value_explorer.js b/src/editor/value_explorer.js
index f1de3be..c83116d 100644
--- a/src/editor/value_explorer.js
+++ b/src/editor/value_explorer.js
@@ -6,10 +6,18 @@
 
 import {el, stringify, scrollIntoViewIfNeeded} from './domutils.js'
 
+
+// We test both for Object and globalThis.run_window.Object because objects may
+// come both from run_window and current window (where they are created in
+// metacircular interpreter
 const has_custom_toString = object =>
   object.toString != globalThis.run_window.Object.prototype.toString
+  &&
+  object.toString != Object.prototype.toString
 
 const isError = object => 
+  object instanceof Error
+  ||
   object instanceof globalThis.run_window.Error
 
 const isPromise = object =>