diff --git a/src/util/misc.js b/src/util/misc.js
index 31b9cf32..0a01d60c 100644
--- a/src/util/misc.js
+++ b/src/util/misc.js
@@ -135,7 +135,7 @@
 
     parseUnit: function(value) {
       var unit = /\D{0,2}$/.exec(value),
-          number = parseFloat(value.slice(0, -unit[0].length));
+          number = parseFloat(value.slice(0, unit.index));
       switch (unit[0]) {
         case 'mm':
           return number * fabric.DPI / 25.4;