diff --git a/addons/web/static/src/js/framework/core.js b/addons/web/static/src/js/framework/core.js
index 4d6d91d907b..9e2dfd964d0 100644
--- a/addons/web/static/src/js/framework/core.js
+++ b/addons/web/static/src/js/framework/core.js
@@ -37,17 +37,6 @@ _.each('resize,scroll'.split(','), function(evtype) {
     });
 });
 
-
-// Underscore customization
-//-------------------------------------------------------------------------
-_.str.toBoolElse = function (str, elseValues, trueValues, falseValues) {
-    var ret = _.str.toBool(str, trueValues, falseValues);
-    if (_.isUndefined(ret)) {
-        return elseValues;
-    }
-    return ret;
-};
-
 // IE patch
 //-------------------------------------------------------------------------
 if (typeof(console) === "undefined") {
diff --git a/addons/web/static/src/js/framework/utils.js b/addons/web/static/src/js/framework/utils.js
index 40774e9095d..edf7355dc29 100644
--- a/addons/web/static/src/js/framework/utils.js
+++ b/addons/web/static/src/js/framework/utils.js
@@ -462,6 +462,15 @@ function swap(array, elem1, elem2) {
     array[i1] = elem2;
 }
 
+function toBoolElse (str, elseValues, trueValues, falseValues) {
+    var ret = _.str.toBool(str, trueValues, falseValues);
+    if (_.isUndefined(ret)) {
+        return elseValues;
+    }
+    return ret;
+}
+
+
 return {
     divmod: divmod,
     modf: modf,
@@ -491,6 +500,7 @@ return {
     reject_after: reject_after,
     delay: delay,
     swap: swap,
+    toBoolElse: toBoolElse,
 };
 
 });
diff --git a/addons/web_calendar/static/src/js/web_calendar.js b/addons/web_calendar/static/src/js/web_calendar.js
index 73abe402dab..e907f09ffd8 100644
--- a/addons/web_calendar/static/src/js/web_calendar.js
+++ b/addons/web_calendar/static/src/js/web_calendar.js
@@ -10,6 +10,7 @@ var form_common = require('web.form_common');
 var formats = require('web.formats');
 var Model = require('web.DataModel');
 var time = require('web.time');
+var utils = require('web.utils');
 var View = require('web.View');
 var widgets = require('web_calendar.widgets');
 var local_storage = require('web.local_storage');
@@ -138,14 +139,14 @@ var CalendarView = View.extend({
         //if quick_add = not specified in view, we use the default quick_create_instance
         //if quick_add = is NOT False and IS specified in view, we this one for quick_create_instance'   
 
-        this.quick_add_pop = (isNullOrUndef(attrs.quick_add) || _.str.toBoolElse(attrs.quick_add, true));
+        this.quick_add_pop = (isNullOrUndef(attrs.quick_add) || utils.toBoolElse(attrs.quick_add, true));
         // The display format which will be used to display the event where fields are between "[" and "]"
         if (!isNullOrUndef(attrs.display)) {
             this.how_display_event = attrs.display; // String with [FIELD]
         }
 
         // If this field is set ot true, we don't open the event in form view, but in a popup with the view_id passed by this parameter
-        if (isNullOrUndef(attrs.event_open_popup) || !_.str.toBoolElse(attrs.event_open_popup, true)) {
+        if (isNullOrUndef(attrs.event_open_popup) || !utils.toBoolElse(attrs.event_open_popup, true)) {
             this.open_popup_action = false;
         } else {
             this.open_popup_action = attrs.event_open_popup;
@@ -155,7 +156,7 @@ var CalendarView = View.extend({
 
         // If this field is set ot true, we don't add itself as an attendee when we use attendee_people to add each attendee icon on an event
         // The color is the color of the attendee, so don't need to show again that it will be present
-        this.colorIsAttendee = !(isNullOrUndef(attrs.color_is_attendee) || !_.str.toBoolElse(attrs.color_is_attendee, true));
+        this.colorIsAttendee = !(isNullOrUndef(attrs.color_is_attendee) || !utils.toBoolElse(attrs.color_is_attendee, true));
 
         // if we have not sidebar, (eg: Dashboard), we don't use the filter "coworkers"
         if (isNullOrUndef(this.options.sidebar)) {
@@ -807,7 +808,7 @@ var CalendarView = View.extend({
                                     value: key,
                                     label: val[1],
                                     color: self.get_color(key),
-                                    avatar_model: (_.str.toBoolElse(self.avatar_filter, true) ? self.avatar_filter : false ),
+                                    avatar_model: (utils.toBoolElse(self.avatar_filter, true) ? self.avatar_filter : false ),
                                     is_checked: true
                                 };
                                 self.all_filters[key] = filter_item;