diff --git a/src/core/2.base.js b/src/core/2.base.js
index 61d9487cc..d7007de52 100644
--- a/src/core/2.base.js
+++ b/src/core/2.base.js
@@ -486,7 +486,7 @@
             if (typeof w === "number") {
                 return w >= 0;
             } else if (typeof w === "string") {
-                return /^\d{1,3}(\.\d)?%$/.test(w) || w === "auto" || /^\d+(\.\d+)px$/.test(w) || /^calc/.test(w);
+                return /^\d{1,3}(\.\d)?%$/.test(w) || w === "auto" || /^\d+(\.\d+)?px$/.test(w) || /^calc/.test(w);
             }
         },