diff --git a/bin/sanitycheck.js b/bin/sanitycheck.js
index 61a251bb5..af0e77126 100755
--- a/bin/sanitycheck.js
+++ b/bin/sanitycheck.js
@@ -10,18 +10,24 @@ apploader.init({
   DEVICEID : "BANGLEJS2"
 });*/
 
+var jsparse = (() => {
+  var acorn, stage3;
+  try {
+    acorn = require("acorn");
+    stage3 = require("acorn-stage3");
+  } catch (e) {
+    console.log("=====================================================");
+    console.log("  ACORN NOT FOUND");
+    console.log("  ---------------");
+    console.log("");
+    console.log("  This means we won't sanity-check uploaded JSON");
+    console.log("=====================================================");
+    return str => {throw new Error("no acorn")};
+  }
 
-var acorn;
-try {
-  acorn = require("acorn");
-} catch (e) {
-  console.log("=====================================================");
-  console.log("  ACORN NOT FOUND");
-  console.log("  ---------------");
-  console.log("");
-  console.log("  This means we won't sanity-check uploaded JSON");
-  console.log("=====================================================");
-}
+  var parser = acorn.Parser.extend(stage3)
+  return str => parser.parse(str, { ecmaVersion: 2020 });
+})();
 
 var BASEDIR = __dirname+"/../";
 var APPSDIR_RELATIVE = "apps/";
@@ -399,7 +405,7 @@ apps.forEach((app,appIdx) => {
     if (file.supports && !Array.isArray(file.supports)) ERROR(`App ${app.id} file ${file.name} supports field is not an array`, {file:metadataFile});
     if (file.evaluate) {
       try {
-        acorn.parse("("+fileContents+")");
+        jsparse("("+fileContents+")");
       } catch(e) {
         console.log("=====================================================");
         console.log("  PARSE OF "+appDir+file.url+" failed.");
@@ -415,7 +421,7 @@ apps.forEach((app,appIdx) => {
       // TODO: actual lint?
       var ast;
       try {
-        ast = acorn.parse(fileContents);
+        ast = jsparse(fileContents);
       } catch(e) {
         console.log("=====================================================");
         console.log("  PARSE OF "+appDir+file.url+" failed.");
diff --git a/package-lock.json b/package-lock.json
index 36589d9eb..f9e7d9bc9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,7 +9,8 @@
       "version": "0.0.1",
       "license": "MIT",
       "dependencies": {
-        "acorn": "^7.2.0"
+        "acorn": "^7.2.0",
+        "acorn-stage3": "^4.0.0"
       },
       "devDependencies": {
         "@typescript-eslint/eslint-plugin": "^7.8.0",
@@ -454,6 +455,21 @@
         "node": ">=0.4.0"
       }
     },
+    "node_modules/acorn-class-fields": {
+      "version": "0.3.7",
+      "resolved": "https://registry.npmjs.org/acorn-class-fields/-/acorn-class-fields-0.3.7.tgz",
+      "integrity": "sha512-jdUWSFce0fuADUljmExz4TWpPkxmRW/ZCPRqeeUzbGf0vFUcpQYbyq52l75qGd0oSwwtAepeL6hgb/naRgvcKQ==",
+      "license": "MIT",
+      "dependencies": {
+        "acorn-private-class-elements": "^0.2.7"
+      },
+      "engines": {
+        "node": ">=4.8.2"
+      },
+      "peerDependencies": {
+        "acorn": "^6 || ^7 || ^8"
+      }
+    },
     "node_modules/acorn-jsx": {
       "version": "5.3.2",
       "resolved": "https://registry.npmjs.org/acorn-jsx/-/acorn-jsx-5.3.2.tgz",
@@ -463,6 +479,65 @@
         "acorn": "^6.0.0 || ^7.0.0 || ^8.0.0"
       }
     },
+    "node_modules/acorn-private-class-elements": {
+      "version": "0.2.7",
+      "resolved": "https://registry.npmjs.org/acorn-private-class-elements/-/acorn-private-class-elements-0.2.7.tgz",
+      "integrity": "sha512-+GZH2wOKNZOBI4OOPmzpo4cs6mW297sn6fgIk1dUI08jGjhAaEwvC39mN2gJAg2lmAQJ1rBkFqKWonL3Zz6PVA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=4.8.2"
+      },
+      "peerDependencies": {
+        "acorn": "^6.1.0 || ^7 || ^8"
+      }
+    },
+    "node_modules/acorn-private-methods": {
+      "version": "0.3.3",
+      "resolved": "https://registry.npmjs.org/acorn-private-methods/-/acorn-private-methods-0.3.3.tgz",
+      "integrity": "sha512-46oeEol3YFvLSah5m9hGMlNpxDBCEkdceJgf01AjqKYTK9r6HexKs2rgSbLK81pYjZZMonhftuUReGMlbbv05w==",
+      "license": "MIT",
+      "dependencies": {
+        "acorn-private-class-elements": "^0.2.7"
+      },
+      "engines": {
+        "node": ">=4.8.2"
+      },
+      "peerDependencies": {
+        "acorn": "^6 || ^7 || ^8"
+      }
+    },
+    "node_modules/acorn-stage3": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/acorn-stage3/-/acorn-stage3-4.0.0.tgz",
+      "integrity": "sha512-BR+LaADtA6GTB5prkNqWmlmCLYmkyW0whvSxdHhbupTaro2qBJ95fJDEiRLPUmiACGHPaYyeH9xmNJWdGfXRQw==",
+      "license": "MIT",
+      "dependencies": {
+        "acorn-class-fields": "^0.3.7",
+        "acorn-private-methods": "^0.3.3",
+        "acorn-static-class-features": "^0.2.4"
+      },
+      "engines": {
+        "node": ">=4.8.2"
+      },
+      "peerDependencies": {
+        "acorn": "^7.4 || ^8"
+      }
+    },
+    "node_modules/acorn-static-class-features": {
+      "version": "0.2.4",
+      "resolved": "https://registry.npmjs.org/acorn-static-class-features/-/acorn-static-class-features-0.2.4.tgz",
+      "integrity": "sha512-5X4mpYq5J3pdndLmIB0+WtFd/mKWnNYpuTlTzj32wUu/PMmEGOiayQ5UrqgwdBNiaZBtDDh5kddpP7Yg2QaQYA==",
+      "license": "MIT",
+      "dependencies": {
+        "acorn-private-class-elements": "^0.2.7"
+      },
+      "engines": {
+        "node": ">=4.8.2"
+      },
+      "peerDependencies": {
+        "acorn": "^6.1.0 || ^7 || ^8"
+      }
+    },
     "node_modules/ajv": {
       "version": "6.12.6",
       "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.12.6.tgz",
@@ -3781,6 +3856,14 @@
       "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.4.1.tgz",
       "integrity": "sha512-nQyp0o1/mNdbTO1PO6kHkwSrmgZ0MT/jCCpNiwbUjGoRN4dlBhqJtoQuCnEOKzgTVwg0ZWiCoQy6SxMebQVh8A=="
     },
+    "acorn-class-fields": {
+      "version": "0.3.7",
+      "resolved": "https://registry.npmjs.org/acorn-class-fields/-/acorn-class-fields-0.3.7.tgz",
+      "integrity": "sha512-jdUWSFce0fuADUljmExz4TWpPkxmRW/ZCPRqeeUzbGf0vFUcpQYbyq52l75qGd0oSwwtAepeL6hgb/naRgvcKQ==",
+      "requires": {
+        "acorn-private-class-elements": "^0.2.7"
+      }
+    },
     "acorn-jsx": {
       "version": "5.3.2",
       "resolved": "https://registry.npmjs.org/acorn-jsx/-/acorn-jsx-5.3.2.tgz",
@@ -3788,6 +3871,38 @@
       "dev": true,
       "requires": {}
     },
+    "acorn-private-class-elements": {
+      "version": "0.2.7",
+      "resolved": "https://registry.npmjs.org/acorn-private-class-elements/-/acorn-private-class-elements-0.2.7.tgz",
+      "integrity": "sha512-+GZH2wOKNZOBI4OOPmzpo4cs6mW297sn6fgIk1dUI08jGjhAaEwvC39mN2gJAg2lmAQJ1rBkFqKWonL3Zz6PVA==",
+      "requires": {}
+    },
+    "acorn-private-methods": {
+      "version": "0.3.3",
+      "resolved": "https://registry.npmjs.org/acorn-private-methods/-/acorn-private-methods-0.3.3.tgz",
+      "integrity": "sha512-46oeEol3YFvLSah5m9hGMlNpxDBCEkdceJgf01AjqKYTK9r6HexKs2rgSbLK81pYjZZMonhftuUReGMlbbv05w==",
+      "requires": {
+        "acorn-private-class-elements": "^0.2.7"
+      }
+    },
+    "acorn-stage3": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/acorn-stage3/-/acorn-stage3-4.0.0.tgz",
+      "integrity": "sha512-BR+LaADtA6GTB5prkNqWmlmCLYmkyW0whvSxdHhbupTaro2qBJ95fJDEiRLPUmiACGHPaYyeH9xmNJWdGfXRQw==",
+      "requires": {
+        "acorn-class-fields": "^0.3.7",
+        "acorn-private-methods": "^0.3.3",
+        "acorn-static-class-features": "^0.2.4"
+      }
+    },
+    "acorn-static-class-features": {
+      "version": "0.2.4",
+      "resolved": "https://registry.npmjs.org/acorn-static-class-features/-/acorn-static-class-features-0.2.4.tgz",
+      "integrity": "sha512-5X4mpYq5J3pdndLmIB0+WtFd/mKWnNYpuTlTzj32wUu/PMmEGOiayQ5UrqgwdBNiaZBtDDh5kddpP7Yg2QaQYA==",
+      "requires": {
+        "acorn-private-class-elements": "^0.2.7"
+      }
+    },
     "ajv": {
       "version": "6.12.6",
       "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.12.6.tgz",
diff --git a/package.json b/package.json
index 57ecf5201..b7de265cd 100644
--- a/package.json
+++ b/package.json
@@ -27,6 +27,7 @@
     "update-local-apps": "apps/*/metadata.json"
   },
   "dependencies": {
-    "acorn": "^7.2.0"
+    "acorn": "^7.2.0",
+    "acorn-stage3": "^4.0.0"
   }
 }