diff --git a/src/Parser.js b/src/Parser.js
index f276521..a637b84 100644
--- a/src/Parser.js
+++ b/src/Parser.js
@@ -1,5 +1,5 @@
 import {COMMENT, RULESET, DECLARATION} from './Enum.js'
-import {abs, trim, from, sizeof, strlen, substr, append, replace, indexof} from './Utility.js'
+import {abs, charat, trim, from, sizeof, strlen, substr, append, replace, indexof} from './Utility.js'
 import {node, char, prev, next, peek, caret, alloc, dealloc, delimit, whitespace, escaping, identifier, commenter} from './Tokenizer.js'
 
 /**
@@ -43,7 +43,7 @@ export function parse (value, root, parent, rule, rules, rulesets, pseudo, point
 		switch (previous = character, character = next()) {
 			// (
 			case 40:
-				if (previous != 108 && characters.charCodeAt(length - 1) == 58) {
+				if (previous != 108 && charat(characters, length - 1) == 58) {
 					if (indexof(characters += replace(delimit(character), '&', '&\f'), '&\f') != -1)
 						ampersand = -1
 					break
diff --git a/src/Utility.js b/src/Utility.js
index a27883b..702fe6e 100644
--- a/src/Utility.js
+++ b/src/Utility.js
@@ -22,7 +22,7 @@ export var assign = Object.assign
  * @return {number}
  */
 export function hash (value, length) {
-	return (((((((length << 2) ^ charat(value, 0)) << 2) ^ charat(value, 1)) << 2) ^ charat(value, 2)) << 2) ^ charat(value, 3)
+	return charat(value, 0) ^ 45 ? (((((((length << 2) ^ charat(value, 0)) << 2) ^ charat(value, 1)) << 2) ^ charat(value, 2)) << 2) ^ charat(value, 3) : 0
 }
 
 /**
diff --git a/test/Prefixer.js b/test/Prefixer.js
index 23ea154..ffb361d 100644
--- a/test/Prefixer.js
+++ b/test/Prefixer.js
@@ -271,4 +271,8 @@ describe('Prefixer', () => {
 	test('tab-size', () => {
 		expect(prefix(`tab-size:1;`, 8)).to.equal([`-moz-tab-size:1;`, `tab-size:1;`].join(''))
 	})
+
+	test('css variables', () => {
+		expect(prefix(`--CircularProgress-animation:0.5s linear;`, 28)).to.equal('--CircularProgress-animation:0.5s linear;')
+	})
 })