diff --git a/NEWS b/NEWS
index 7476e7b71..81ef32b12 100644
--- a/NEWS
+++ b/NEWS
@@ -25,6 +25,7 @@ Bug fixes
  - [web] fixed saving draft outside Mail module (#4071)
  - [web] fixed SCAYT automatic language selection in HTML editor
  - [web] fixed task sorting on multiple categories
+ - [web] fixed sanitisation of flags in Sieve filters (#4087)
  - [eas] fixed opacity in EAS freebusy (#4033)
 
 3.2.7 (2017-02-14)
diff --git a/UI/WebServerResources/js/Preferences/Preferences.service.js b/UI/WebServerResources/js/Preferences/Preferences.service.js
index 2b92b6da1..b0ae12eb2 100644
--- a/UI/WebServerResources/js/Preferences/Preferences.service.js
+++ b/UI/WebServerResources/js/Preferences/Preferences.service.js
@@ -22,9 +22,16 @@
           return ['_' + key, value];
         return [key, value];
       }));
-
       data.SOGoMailLabelsColors = labels;
 
+      _.forEach(data.SOGoSieveFilters, function(filter) {
+        _.forEach(filter.actions, function(action) {
+          if (action.method == 'addflag' &&
+              action.argument.charAt(0) == '$')
+            action.argument = '_' + action.argument;
+        });
+      });
+
       if (data.SOGoRememberLastModule)
         data.SOGoLoginModule = "Last";
 
@@ -260,9 +267,17 @@
       }
       return [key, value];
     }));
-
     preferences.defaults.SOGoMailLabelsColors = labels;
 
+    _.forEach(preferences.defaults.SOGoSieveFilters, function(filter) {
+      _.forEach(filter.actions, function(action) {
+        if (action.method == 'addflag' &&
+            action.argument.charAt(0) == '_' &&
+            action.argument.charAt(1) == '$')
+          action.argument = action.argument.substring(1);
+      });
+    });
+
     if (!preferences.defaults.SOGoMailComposeFontSizeEnabled)
       preferences.defaults.SOGoMailComposeFontSize = 0;
     delete preferences.defaults.SOGoMailComposeFontSizeEnabled;