diff --git a/lib/pixel-unit-regex.js b/lib/pixel-unit-regex.js
index 7115052..87d656e 100644
--- a/lib/pixel-unit-regex.js
+++ b/lib/pixel-unit-regex.js
@@ -6,4 +6,4 @@
 // Any digit followed by px
 // !singlequotes|!doublequotes|!url()|pixelunit
 
-module.exports = /"[^"]+"|'[^']+'|url\([^)]+\)|var\([^)]+\)|(\d*\.?\d+)px/g;
+module.exports = /"[^"]+"|'[^']+'|url\([^)]+\)|((?<=^|[^\w-])-?\d*\.?\d+)px\b/g;