diff --git a/extension/lite/execution/ext/ui/create.html.php b/extension/lite/execution/ext/ui/create.html.php
index ae0f06e6cb..4685cf2991 100644
--- a/extension/lite/execution/ext/ui/create.html.php
+++ b/extension/lite/execution/ext/ui/create.html.php
@@ -35,8 +35,8 @@ formPanel
             $lang->execution->copy
         )
     ),
-    on::change('[name=begin]', 'computeWorkDays'),
-    on::change('[name=end]', 'computeWorkDays'),
+    on::change('[name=begin]', 'computeWorkDays(NaN)'),
+    on::change('[name=end]', 'computeWorkDays(NaN)'),
     $config->systemMode == 'ALM' ? formGroup
     (
         set::width('1/2'),