diff --git a/src/Composer/Util/StreamContextFactory.php b/src/Composer/Util/StreamContextFactory.php
index e177059d3..b8290086c 100644
--- a/src/Composer/Util/StreamContextFactory.php
+++ b/src/Composer/Util/StreamContextFactory.php
@@ -55,7 +55,7 @@ final class StreamContextFactory
         }
 
         // Remove proxy if URL matches no_proxy directive
-        if (!empty($_SERVER['NO_PROXY']) || $_SERVER['no_proxy']) && parse_url($url, PHP_URL_HOST)) {
+        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);