diff --git a/package.json b/package.json
index ca40f1e..234c07f 100644
--- a/package.json
+++ b/package.json
@@ -9,8 +9,8 @@
   "scripts": {
     "build": "tsc",
     "build-worker": "node worker/build.js",
-    "test": "npm run-script build-worker && node --experimental-vm-modules node_modules/jest/bin/jest.js --verbose --collectCoverage --coverageProvider=v8",
-    "test-debug": "npm run-script build-worker && node --experimental-vm-modules --inspect-brk node_modules/jest/bin/jest.js --runInBand",
+    "test": "npm run-script build-worker && node --no-experimental-fetch --experimental-vm-modules node_modules/jest/bin/jest.js --verbose --collectCoverage --coverageProvider=v8",
+    "test-debug": "npm run-script build-worker && node --no-experimental-fetch --experimental-vm-modules --inspect-brk node_modules/jest/bin/jest.js --runInBand",
     "format": "prettier --write  '*.{json,js}' 'src/**/*.{js,ts}' 'test/**/*.{js,ts}'",
     "lint": "eslint --max-warnings=0 src && prettier --check '*.{json,js}' 'src/**/*.{js,ts}' 'test/**/*.{js,ts}'",
     "prepack": "npm run-script test && npm run-script lint && npm run-script build",
@@ -111,4 +111,4 @@
   "dependencies": {
     "worktop": "0.7.3"
   }
-}
+}
\ No newline at end of file
diff --git a/src/processConditionals.ts b/src/processConditionals.ts
index 0a381d1..2a8beaa 100644
--- a/src/processConditionals.ts
+++ b/src/processConditionals.ts
@@ -125,16 +125,25 @@ function esi_eval_var_in_when_tag(
   match: [String: string, ...args: string[]],
 ): string {
   const varInTag = esi_eval_var(eventData, match);
-
-  const number = parseInt(varInTag, 10);
-  if (number) {
-    return number.toString();
+  // we have to check varInTag is *actually* a number and doesn't just have leading numbers in it
+  if (strIsNumber(varInTag)) {
+    return parseInt(varInTag, 10).toString();
   } else {
     // Change to replaceAll once upgraded node
     return "'" + varInTag.replace(/'/g, "\\'") + "'";
   }
 }
 
+/**
+ * Evaluates str and returns if it *actually* is a number not just a str with leading numbers
+ *
+ * @param {string} str string to check
+ * @returns {boolean} check result
+ */
+function strIsNumber(str: string): boolean {
+  return !isNaN(Number(str))
+}
+
 /**
  * Takes a condition string and splits it into its two sides and operator
  * passes that to the tester and returns the result
diff --git a/test/esi.spec.ts b/test/esi.spec.ts
index f0d97c5..9c4ce7b 100644
--- a/test/esi.spec.ts
+++ b/test/esi.spec.ts
@@ -579,6 +579,7 @@ test("TEST 9e: List variable syntax (accept-language) with multiple headers", as
   );
 
   const res = await makeRequest(`${url}?t=1`, {
+    // @ts-ignore
     headers: {
       // @ts-ignore
       "Accept-Language": ["da, en-gb", "fr"],
@@ -1063,6 +1064,7 @@ test("TEST 20b: Test we advertise Surrogate-Capability (with COLO Data)", async
     res.writeHead(200, esiHead);
     res.end(req.headers["surrogate-capability"]);
   });
+  // @ts-ignore
   const res = await makeRequest(url, { cf: { colo: "DFW" } });
   expect(res.ok).toBeTruthy();
   expect(checkSurrogate(res)).toBeTruthy();
@@ -1911,3 +1913,33 @@ test("TEST 50: Multiple ESI Args make it all the way through", async () => {
     `esi_args1=1&esi_args2=2&esi_args3=3&esi_args4=4`,
   );
 });
+
+describe("TEST 51: ESI Args that lead with ints shouldn't convert to ints", () => {
+  const checks = [
+    { arg: "1719,2405", result: "first-lineage" },
+    { arg: "1719,1732", result: "second-lineage" },
+    { arg: "1719,1918", result: "third-lineage" },
+    { arg: "1719,1922", result: "forth-lineage" },
+    { arg: "1719,1926", result: "fith-lineage" },
+  ];
+
+  const url = `/esi/test-51`;
+  checks.forEach(function (check) {
+    it(check.result, async () => {
+      routeHandler.add(url, function (req, res) {
+        res.writeHead(200, esiHead);
+        res.end(`
+    first-lineage
+    second-lineage
+    third-lineage
+    forth-lineage
+    fith-lineage
+`);
+      });
+      const res = await makeRequest(`${url}?esi_lineage=${check.arg}`);
+      expect(res.ok).toBeTruthy();
+      expect(await res.text()).toEqual(check.result);
+      expect(checkSurrogate(res)).toBeTruthy();
+    });
+  });
+});