diff --git a/lib/css/walkCssTokens.js b/lib/css/walkCssTokens.js
index ea97ca0d3..d2bd70f16 100644
--- a/lib/css/walkCssTokens.js
+++ b/lib/css/walkCssTokens.js
@@ -66,7 +66,7 @@ const CC_LOWER_Z = "z".charCodeAt(0);
 const CC_UPPER_A = "A".charCodeAt(0);
 const CC_UPPER_F = "F".charCodeAt(0);
 const CC_UPPER_E = "E".charCodeAt(0);
-const CC_UPPER_U = "E".charCodeAt(0);
+const CC_UPPER_U = "U".charCodeAt(0);
 const CC_UPPER_Z = "Z".charCodeAt(0);
 const CC_0 = "0".charCodeAt(0);
 const CC_9 = "9".charCodeAt(0);