diff --git a/dist/index.js b/dist/index.js
index c47858f..c4f5f72 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -103364,7 +103364,7 @@ ${stderrBuffer}`
     }
     if (this.extraArgs) {
       const extraArgs = parseArgsStringToArgv(this.extraArgs);
-      args.concat(extraArgs);
+      args.push(...extraArgs);
     }
     this.recordEvent(EVENT_INSTALL_NIX_START);
     const exitCode = await exec.exec(binaryPath, args, {
diff --git a/src/index.ts b/src/index.ts
index 748c277..5f09ab0 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -570,7 +570,7 @@ class NixInstallerAction extends DetSysAction {
 
     if (this.extraArgs) {
       const extraArgs = stringArgv(this.extraArgs);
-      args.concat(extraArgs);
+      args.push(...extraArgs);
     }
 
     this.recordEvent(EVENT_INSTALL_NIX_START);