diff --git a/typescript/src/ts/program.ts b/typescript/src/ts/program.ts
index 5fc21b5d..712d00cc 100644
--- a/typescript/src/ts/program.ts
+++ b/typescript/src/ts/program.ts
@@ -98,7 +98,7 @@ function isValidFunctionName(name: unknown): name is string {
  */
 export function createModuleTextFromProgram(jsonObject: object): Result<string> {
     const steps = (jsonObject as Program)["@steps"];
-    if (!(Array.isArray(steps) && steps.every(step => typeof step === "object" && step !== null && step.hasOwnProperty("@func")))) {
+    if (!(Array.isArray(steps) && steps.every(step => typeof step === "object" && step !== null && Object.prototype.hasOwnProperty.call(step, "@func")))) {
         return error("JSON object is not a valid program");
     }
     let hasError = false;
@@ -119,15 +119,15 @@ export function createModuleTextFromProgram(jsonObject: object): Result<string>
     }
 
     function objectToString(obj: Record<string, unknown>) {
-        if (obj.hasOwnProperty("@ref")) {
+        if (Object.prototype.hasOwnProperty.call(obj, "@ref")) {
             const index = obj["@ref"];
             if (typeof index === "number" && Number.isInteger(index) && index >= 0 && index < currentStep && Object.keys(obj).length === 1) {
                 return `step${index + 1}`;
             }
         }
-        else if (obj.hasOwnProperty("@func")) {
+        else if (Object.prototype.hasOwnProperty.call(obj, "@func")) {
             const func = obj["@func"];
-            const hasArgs = obj.hasOwnProperty("@args");
+            const hasArgs = Object.prototype.hasOwnProperty.call(obj, "@args");
             const args = hasArgs ? obj["@args"] : [];
             if (isValidFunctionName(func) && (Array.isArray(args)) && Object.keys(obj).length === (hasArgs ? 2 : 1)) {
                 return `api.${func}(${arrayToString(args)})`;
@@ -171,16 +171,16 @@ export async function evaluateJsonProgram(program: Program, onCall: (func: strin
     }
 
     async function evaluateObject(obj: Record<string, unknown>) {
-        if (obj.hasOwnProperty("@ref")) {
+        if (Object.prototype.hasOwnProperty.call(obj, "@ref")) {
             const index = obj["@ref"];
             if (Object.keys(obj).length === 1 && typeof index === "number" && Number.isInteger(index) && index >= 0 && index < results.length) {
                 return results[index];
             }
             throw new Error(`Invalid result reference: ${String(index)}`);
         }
-        else if (obj.hasOwnProperty("@func")) {
+        else if (Object.prototype.hasOwnProperty.call(obj, "@func")) {
             const func = obj["@func"];
-            const hasArgs = obj.hasOwnProperty("@args");
+            const hasArgs = Object.prototype.hasOwnProperty.call(obj, "@args");
             const args = hasArgs ? obj["@args"] : [];
             if (!isValidFunctionName(func)) {
                 throw new Error(`Invalid function name: ${JSON.stringify(func)}`);
diff --git a/typescript/test/program.test.ts b/typescript/test/program.test.ts
index b95515bb..53ba9a0b 100644
--- a/typescript/test/program.test.ts
+++ b/typescript/test/program.test.ts
@@ -2,6 +2,39 @@ import { describe, it } from "node:test";
 import assert from "node:assert/strict";
 import { evaluateJsonProgram, createModuleTextFromProgram, Program, FunctionCall } from "../dist/ts/index.js";
 
+describe("program objects with own property names", () => {
+    const programs: Array<[string, Program]> = [
+        ["a literal hasOwnProperty field", {
+            "@steps": [{ "@func": "identity", "@args": [{ hasOwnProperty: "user data", value: 7 }] }],
+        }],
+        ["a null-prototype call and argument", {
+            "@steps": [Object.assign(Object.create(null), {
+                "@func": "identity",
+                "@args": [Object.assign(Object.create(null), { hasOwnProperty: "user data", value: 7 })],
+            })],
+        }],
+    ];
+
+    for (const [name, program] of programs) {
+        it(`generates a module for ${name}`, () => {
+            const result = createModuleTextFromProgram(program);
+            assert.ok(result.success);
+            assert.equal(result.data,
+                'import { API } from "./schema";\nfunction program(api: API) {\n' +
+                '  return api.identity({ "hasOwnProperty": "user data", "value": 7 });\n}');
+        });
+
+        it(`evaluates ${name} without losing the argument`, async () => {
+            const result = await evaluateJsonProgram(program, async (func, args) => {
+                assert.equal(func, "identity");
+                assert.deepEqual(args, [{ hasOwnProperty: "user data", value: 7 }]);
+                return args[0];
+            });
+            assert.deepEqual(result, { hasOwnProperty: "user data", value: 7 });
+        });
+    }
+});
+
 // ---------------------------------------------------------------------------
 // evaluateJsonProgram result-reference bounds checking
 // ---------------------------------------------------------------------------