diff --git a/src/evalfunc.c b/src/evalfunc.c
index af43fb9..f192506 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2015,6 +2015,12 @@
 	    return;
 	++list->lv_refcount;
     }
+    else if (argvars[arg_off].v_type == VAR_JOB
+	    || argvars[arg_off].v_type == VAR_CHANNEL)
+    {
+	emsg(_(e_inval_string));
+	return;
+    }
     else
     {
 	cmd = tv_get_string_chk(&argvars[arg_off]);