diff --git a/src/Terminal.ts b/src/Terminal.ts
index e441a5b4..3144ae93 100644
--- a/src/Terminal.ts
+++ b/src/Terminal.ts
@@ -2169,7 +2169,9 @@ export class Terminal extends EventEmitter implements ITerminal, IInputHandlingT
     this._customKeyEventHandler = customKeyEventHandler;
     this._inputHandler = inputHandler;
     this.refresh(0, this.rows - 1);
-    this.viewport.syncScrollArea();
+    if (this.viewport) {
+      this.viewport.syncScrollArea();
+    }
   }