diff --git a/src/Message/Uri.php b/src/Message/Uri.php
index 4309bbed..1eaf24fe 100644
--- a/src/Message/Uri.php
+++ b/src/Message/Uri.php
@@ -55,7 +55,7 @@ public function __construct($uri)
         }
         // @codeCoverageIgnoreEnd
 
-        if ($parts === false || (isset($parts['scheme']) && !\preg_match('#^[a-z]+$#i', $parts['scheme'])) || (isset($parts['host']) && \preg_match('#[\s_%+]#', $parts['host']))) {
+        if ($parts === false || (isset($parts['scheme']) && !\preg_match('#^[a-z]+$#i', $parts['scheme'])) || (isset($parts['host']) && \preg_match('#[\s%+]#', $parts['host']))) {
             throw new \InvalidArgumentException('Invalid URI given');
         }
 
@@ -173,7 +173,7 @@ public function withHost($host)
             return $this;
         }
 
-        if (\preg_match('#[\s_%+]#', $host) || ($host !== '' && \parse_url('http://' . $host, \PHP_URL_HOST) !== $host)) {
+        if (\preg_match('#[\s%+]#', $host) || ($host !== '' && \parse_url('http://' . $host, \PHP_URL_HOST) !== $host)) {
             throw new \InvalidArgumentException('Invalid URI host given');
         }
 
diff --git a/tests/Message/UriTest.php b/tests/Message/UriTest.php
index 05eec723..1ed6abf2 100644
--- a/tests/Message/UriTest.php
+++ b/tests/Message/UriTest.php
@@ -120,7 +120,10 @@ public static function provideValidUris()
             ),
             array(
                 'http://user%20name:pass%20word@localhost/path%20name?query%20name#frag%20ment'
-            )
+            ),
+            array(
+                'http://docker_container/'
+            ),
         );
     }