diff --git a/doc/03-cli.md b/doc/03-cli.md
index 1daae9154..aff1bce30 100644
--- a/doc/03-cli.md
+++ b/doc/03-cli.md
@@ -815,10 +815,10 @@ similar use case), and need to support proxies, please provide the `CGI_HTTP_PRO
 environment variable instead. See [httpoxy.org](https://httpoxy.org/) for further
 details.
 
-### no_proxy
+### no_proxy or NO_PROXY
 
 If you are behind a proxy and would like to disable it for certain domains, you
-can use the `no_proxy` env var. Simply set it to a comma separated list of
+can use the `no_proxy` or `NO_PROXY` env var. Simply set it to a comma separated list of
 domains the proxy should *not* be used for.
 
 The env var accepts domains, IP addresses, and IP address blocks in CIDR
diff --git a/src/Composer/Util/StreamContextFactory.php b/src/Composer/Util/StreamContextFactory.php
index 911bb36a1..b8290086c 100644
--- a/src/Composer/Util/StreamContextFactory.php
+++ b/src/Composer/Util/StreamContextFactory.php
@@ -55,8 +55,8 @@ final class StreamContextFactory
         }
 
         // Remove proxy if URL matches no_proxy directive
-        if (!empty($_SERVER['no_proxy']) && parse_url($url, PHP_URL_HOST)) {
-            $pattern = new NoProxyPattern($_SERVER['no_proxy']);
+        if (!empty($_SERVER['NO_PROXY']) || !empty($_SERVER['no_proxy']) && parse_url($url, PHP_URL_HOST)) {
+            $pattern = new NoProxyPattern(!empty($_SERVER['no_proxy']) ? $_SERVER['no_proxy'] : $_SERVER['NO_PROXY']);
             if ($pattern->test($url)) {
                 unset($proxy);
             }
diff --git a/tests/Composer/Test/Util/StreamContextFactoryTest.php b/tests/Composer/Test/Util/StreamContextFactoryTest.php
index 93cf881e2..0618675a2 100644
--- a/tests/Composer/Test/Util/StreamContextFactoryTest.php
+++ b/tests/Composer/Test/Util/StreamContextFactoryTest.php
@@ -22,6 +22,7 @@ class StreamContextFactoryTest extends \PHPUnit_Framework_TestCase
         unset($_SERVER['http_proxy']);
         unset($_SERVER['HTTPS_PROXY']);
         unset($_SERVER['https_proxy']);
+        unset($_SERVER['NO_PROXY']);
         unset($_SERVER['no_proxy']);
     }
 
@@ -31,6 +32,7 @@ class StreamContextFactoryTest extends \PHPUnit_Framework_TestCase
         unset($_SERVER['http_proxy']);
         unset($_SERVER['HTTPS_PROXY']);
         unset($_SERVER['https_proxy']);
+        unset($_SERVER['NO_PROXY']);
         unset($_SERVER['no_proxy']);
     }