diff --git a/app/imports/api/engine/computation/writeComputation/writeScope.js b/app/imports/api/engine/computation/writeComputation/writeScope.js
index 6d0aecbc..3bb550f8 100644
--- a/app/imports/api/engine/computation/writeComputation/writeScope.js
+++ b/app/imports/api/engine/computation/writeComputation/writeScope.js
@@ -4,7 +4,8 @@ import { EJSON } from 'meteor/ejson';
 export default function writeScope(creatureId, computation) {
   const scope = computation.scope;
   const variables = computation.creature?.variables || {};
-  let $set;
+  let $set, $unset;
+
   for (const key in scope){
     // Remove large properties that aren't likely to be accessed
     delete scope[key].parent;
@@ -24,7 +25,16 @@ export default function writeScope(creatureId, computation) {
       $set[`variables.${key}`] = scope[key];
     }
   }
-  if ($set) {
-    Creatures.update(creatureId, {$set});
+
+  // Remove all the keys that no longer exist in scope
+  for (const key in variables) {
+    if (!scope[key]) {
+      if (!$unset) $unset = {};
+      $unset[`variables.${key}`] = 1;
+    }
+  }
+
+  if ($set || $unset) {
+    Creatures.update(creatureId, {$set, $unset});
   }
 }