diff --git a/lib/main.js b/lib/main.js
index 7b4e63a..c873cc7 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -1,10 +1,10 @@
 'use strict'
 
 function _interpolate (envValue, environment, config) {
-  const matches = envValue.match(/(.?\${*[\w]*(?::-)?[\w]*}*)/g) || []
+  const matches = envValue.match(/(.?\${*[\w]*(?::-[\w/]*)?}*)/g) || []
 
   return matches.reduce(function (newEnv, match, index) {
-    const parts = /(.?)\${*([\w]*(?::-)?[\w]*)?}*/g.exec(match)
+    const parts = /(.?)\${*([\w]*(?::-[\w/]*)?)?}*/g.exec(match)
     if (!parts || parts.length === 0) {
       return newEnv
     }