diff --git a/src/vim9compile.c b/src/vim9compile.c
index d7c7c8b..117bfd2 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -3678,6 +3678,7 @@
 	    // eval the next expression
 	    *arg = skipwhite(p + 2);
 	    tv2.v_type = VAR_UNKNOWN;
+	    tv2.v_lock = 0;
 	    if ((opchar == '|' ? evaluate_const_expr3(arg, cctx, &tv2)
 			       : evaluate_const_expr7(arg, cctx, &tv2)) == FAIL)
 	    {