diff --git a/src/common/CoreTerminal.ts b/src/common/CoreTerminal.ts
index 9bd7faaf5..80168aa65 100644
--- a/src/common/CoreTerminal.ts
+++ b/src/common/CoreTerminal.ts
@@ -263,7 +263,7 @@ export abstract class CoreTerminal extends Disposable implements ICoreTerminal {
   private _handleWindowsPtyOptionChange(): void {
     let value = false;
     const windowsPty = this.optionsService.rawOptions.windowsPty;
-    if (windowsPty && windowsPty.buildNumber !== undefined && windowsPty.buildNumber !== undefined) {
+    if (windowsPty && windowsPty.backend !== undefined && windowsPty.buildNumber !== undefined) {
       value = !!(windowsPty.backend === 'conpty' && windowsPty.buildNumber < 21376);
     }
     if (value) {