diff --git a/src/channel.c b/src/channel.c
index 08b1ac8..4e64575 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -2872,8 +2872,14 @@
 
     buffer->b_p_ma = TRUE;
 
-    // set curbuf to be our buf, temporarily
+    // Set curbuf to "buffer", temporarily.
     aucmd_prepbuf(&aco, buffer);
+    if (curbuf != buffer)
+    {
+	// Could not find a window for this buffer, the following might cause
+	// trouble, better bail out.
+	return;
+    }
 
     u_sync(TRUE);
     // ignore undo failure, undo is not very useful here