diff --git a/src/core/4.widget.js b/src/core/4.widget.js
index 61b09a07b..4ca395207 100644
--- a/src/core/4.widget.js
+++ b/src/core/4.widget.js
@@ -225,7 +225,7 @@
                 if (BI.isFunction(o.css)) {
                     var css = this.__watch(o.css, function (context, newValue) {
                         for (var k in css) {
-                            if (!newValue[k]) {
+                            if (BI.isNull(newValue[k])) {
                                 newValue[k] = "";
                             }
                         }