diff --git a/src/unixTerminal.test.ts b/src/unixTerminal.test.ts
index a666e91a..c6378008 100644
--- a/src/unixTerminal.test.ts
+++ b/src/unixTerminal.test.ts
@@ -18,7 +18,37 @@ const FIXTURES_PATH = path.normalize(path.join(__dirname, '..', 'fixtures', 'utf
 if (process.platform !== 'win32') {
   // Dynamic require to avoid loading pty.node on Windows
   // eslint-disable-next-line @typescript-eslint/naming-convention
-  const { UnixTerminal } = require('./unixTerminal') as { UnixTerminal: typeof UnixTerminalType };
+  const { UnixTerminal, resolveSpawnHelperPath } = require('./unixTerminal') as { UnixTerminal: typeof UnixTerminalType; resolveSpawnHelperPath: (nativeDir: string, moduleDir: string) => string };
+
+  describe('resolveSpawnHelperPath', () => {
+    it('rewrites a packed asar path to its unpacked form', () => {
+      const helperPath = resolveSpawnHelperPath(
+        '/Example.app/Contents/Resources/app.asar/node_modules/node-pty/build/Release',
+        '/Example.app/Contents/Resources/app.asar/node_modules/node-pty/lib');
+      assert.strictEqual(helperPath, '/Example.app/Contents/Resources/app.asar.unpacked/node_modules/node-pty/build/Release/spawn-helper');
+    });
+
+    it('does not double-rewrite an already-unpacked asar path', () => {
+      const helperPath = resolveSpawnHelperPath(
+        '/Example.app/Contents/Resources/app.asar.unpacked/node_modules/node-pty/build/Release',
+        '/Example.app/Contents/Resources/app.asar.unpacked/node_modules/node-pty/lib');
+      assert.strictEqual(helperPath, '/Example.app/Contents/Resources/app.asar.unpacked/node_modules/node-pty/build/Release/spawn-helper');
+    });
+
+    it('rewrites a packed node_modules.asar path to its unpacked form', () => {
+      const helperPath = resolveSpawnHelperPath(
+        '/app/node_modules.asar/node-pty/build/Release',
+        '/app/node_modules.asar/node-pty/lib');
+      assert.strictEqual(helperPath, '/app/node_modules.asar.unpacked/node-pty/build/Release/spawn-helper');
+    });
+
+    it('does not double-rewrite an already-unpacked node_modules.asar path', () => {
+      const helperPath = resolveSpawnHelperPath(
+        '/app/node_modules.asar.unpacked/node-pty/build/Release',
+        '/app/node_modules.asar.unpacked/node-pty/lib');
+      assert.strictEqual(helperPath, '/app/node_modules.asar.unpacked/node-pty/build/Release/spawn-helper');
+    });
+  });
 
   describe('UnixTerminal', () => {
     describe('Constructor', () => {
diff --git a/src/unixTerminal.ts b/src/unixTerminal.ts
index 2776d501..44d202b8 100644
--- a/src/unixTerminal.ts
+++ b/src/unixTerminal.ts
@@ -14,10 +14,32 @@ import { assign, loadNativeModule } from './utils';
 
 const native = loadNativeModule('pty');
 const pty: IUnixNative = native.module;
-let helperPath = native.dir + '/spawn-helper';
-helperPath = path.resolve(__dirname, helperPath);
-helperPath = helperPath.replace('app.asar', 'app.asar.unpacked');
-helperPath = helperPath.replace('node_modules.asar', 'node_modules.asar.unpacked');
+
+/**
+ * Resolve the absolute path of the platform spawn helper binary.
+ *
+ * @param nativeDir - the directory that holds the compiled native module.
+ * @param moduleDir - the directory of this module (resolves relative dirs).
+ * @returns the absolute spawn-helper path.
+ */
+export function resolveSpawnHelperPath(nativeDir: string, moduleDir: string): string {
+  let helperPath = path.resolve(moduleDir, nativeDir + '/spawn-helper');
+  // String.prototype.replace matches the first occurrence, so when helperPath
+  // already contains 'app.asar.unpacked' (e.g. node-pty is installed under an
+  // unpacked asar directory) the substring 'app.asar' matches the prefix of
+  // 'app.asar.unpacked' and produces 'app.asar.unpacked.unpacked' — a path
+  // that does not exist on disk. Skip each rewrite when the unpacked variant
+  // is already present.
+  if (helperPath.indexOf('app.asar.unpacked') === -1) {
+    helperPath = helperPath.replace('app.asar', 'app.asar.unpacked');
+  }
+  if (helperPath.indexOf('node_modules.asar.unpacked') === -1) {
+    helperPath = helperPath.replace('node_modules.asar', 'node_modules.asar.unpacked');
+  }
+  return helperPath;
+}
+
+const helperPath = resolveSpawnHelperPath(native.dir, __dirname);
 
 const DEFAULT_FILE = 'sh';
 const DEFAULT_NAME = 'xterm';