diff --git a/src/vim9cmds.c b/src/vim9cmds.c
index a853d9b..ad32c32 100644
--- a/src/vim9cmds.c
+++ b/src/vim9cmds.c
@@ -2125,7 +2125,7 @@
 	    generate_instr_type(cctx, ISN_REDIREND, &t_string);
 
 	    if (lhs->lhs_append)
-		generate_instr_drop(cctx, ISN_CONCAT, 1);
+		generate_CONCAT(cctx, 2);
 
 	    if (lhs->lhs_has_index)
 	    {