diff --git a/app/controllers/measurements_controller.rb b/app/controllers/measurements_controller.rb
index 9de8107..2b7e7a6 100644
--- a/app/controllers/measurements_controller.rb
+++ b/app/controllers/measurements_controller.rb
@@ -80,7 +80,7 @@ class MeasurementsController < ApplicationController
   private
 
   def init_session_filters
-    session[:m_filters] ||= {}
+    session[:m_filters] ||= {formula: {}}
   end
 
   def measurement_params
diff --git a/app/views/measurements/_filters.html.erb b/app/views/measurements/_filters.html.erb
index 5d53a83..328f95b 100644
--- a/app/views/measurements/_filters.html.erb
+++ b/app/views/measurements/_filters.html.erb
@@ -13,11 +13,16 @@
             onblur: '$("#filters-form").submit(); return false;' %>
         </td>
         <td style="width:100%;">
-          <%= text_field_tag 'filters[formula]', session[:m_filters][:formula],
+          <%= text_field_tag 'filters[formula][code]', session[:m_filters][:formula][:code],
             placeholder: 'conditional expression including readouts', size: 40,
             style: 'box-sizing:border-box; width:100%;',
             onblur: '$("#filters-form").submit(); return false;' %>
         </td>
+        <td>
+          <%= check_box_tag 'filters[formula][zero_nil]',
+            session[:m_filters][:formula][:zero_nil] %>
+          <%= t '.zero_nil' %>
+        </td>
         <td>
           <%= link_to l(:button_apply), '#', class: "icon icon-checked",
             onclick: '$("#filters-form").submit(); return false;' %>
diff --git a/config/locales/en.yml b/config/locales/en.yml
index b000a28..797e84d 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -62,6 +62,8 @@ en:
   measurements:
     contextual:
       link_new_measurement: 'New measurement'
+    filters:
+      zero_nil: 'missing -> 0?'
     form:
       button_new_readout: 'Add readout'
       button_delete_readout: 'Delete'