diff --git a/src/evalwindow.c b/src/evalwindow.c
index 00081d4..f9b1c12 100644
--- a/src/evalwindow.c
+++ b/src/evalwindow.c
@@ -824,6 +824,13 @@
 	return;
 
     id = tv_get_number(&argvars[0]);
+    if (curwin->w_id == id)
+    {
+	// Nothing to do.
+	rettv->vval.v_number = 1;
+	return;
+    }
+
     if (text_or_buf_locked())
 	return;
 #if defined(FEAT_PROP_POPUP) && defined(FEAT_TERMINAL)