diff --git a/plugin/qfdiagnostics.vim b/plugin/qfdiagnostics.vim
index bfb1381..ec5b10e 100644
--- a/plugin/qfdiagnostics.vim
+++ b/plugin/qfdiagnostics.vim
@@ -1,3 +1,7 @@
+if !has('vim9script') ||  v:version < 900
+  finish
+endif
+
 vim9script
 # ==============================================================================
 # Highlight quickfix locations and show error messages in popup window