diff --git a/PHPCI/Plugin/Env.php b/PHPCI/Plugin/Env.php
index 1de016fb..e09d3dbf 100644
--- a/PHPCI/Plugin/Env.php
+++ b/PHPCI/Plugin/Env.php
@@ -41,7 +41,7 @@ class Env implements \PHPCI\Plugin
                 $env_var = "$key=$value";
             }
             
-            if (!putenv($env_var)) {
+            if (!putenv($this->phpci->interpolate($env_var))) {
                 $success = false;
                 $this->phpci->logFailure("Unable to set environment variable");
             }