diff --git a/src/kernelCoreTemplate.js b/src/kernelCoreTemplate.js
index c9916f0889c17f850bffe8e5c02b3f804c9ed810..55edb49c936f28b928f74150c748fe80a9add896 100644
--- a/src/kernelCoreTemplate.js
+++ b/src/kernelCoreTemplate.js
@@ -138,9 +138,9 @@
           continue
         }
         let desc = Object.getOwnPropertyDescriptor(globalRef, prop)
-        if (desc?.configurable === true) {
+        if (desc && desc.configurable === true) {
           desc = { configurable: false, set, get }
-        } else if (desc?.writable === true) {
+        } else if (desc && desc.writable === true) {
           const p = new Proxy(obj, { getPrototypeOf: get, get, set } )
           desc = { configurable: false, writable: false, value: p }
         } else {