diff --git a/src/evalvars.c b/src/evalvars.c
index eb69d3e..260c297 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -759,6 +759,11 @@
 	semsg(_(e_str_cannot_be_used_in_legacy_vim_script), ":var");
 	return;
     }
+    if (current_sctx.sc_sid == 0)
+    {
+	emsg(_(e_cannot_declare_variable_on_command_line));
+	return;
+    }
     ex_let(eap);
 }
 
@@ -3440,7 +3445,7 @@
 	if (in_vim9script() && is_export
 		&& SCRIPT_ID_VALID(current_sctx.sc_sid)
 		&& (si = SCRIPT_ITEM(current_sctx.sc_sid))
-						   ->sn_autoload_prefix != NULL)
+						  ->sn_autoload_prefix != NULL)
 	{
 	    // In a vim9 autoload script an exported variable is put in the
 	    // global namespace with the autoload prefix.