diff --git a/src/Uri.php b/src/Uri.php
index 2085ab73..825a25ee 100644
--- a/src/Uri.php
+++ b/src/Uri.php
@@ -628,9 +628,9 @@ private function filterPort($port)
         }
 
         $port = (int) $port;
-        if (1 > $port || 0xffff < $port) {
+        if (0 > $port || 0xffff < $port) {
             throw new \InvalidArgumentException(
-                sprintf('Invalid port: %d. Must be between 1 and 65535', $port)
+                sprintf('Invalid port: %d. Must be between 0 and 65535', $port)
             );
         }
 
diff --git a/tests/UriTest.php b/tests/UriTest.php
index 8a9141eb..b9fb7e81 100644
--- a/tests/UriTest.php
+++ b/tests/UriTest.php
@@ -117,7 +117,7 @@ public function getInvalidUris()
 
     /**
      * @expectedException \InvalidArgumentException
-     * @expectedExceptionMessage Invalid port: 100000. Must be between 1 and 65535
+     * @expectedExceptionMessage Invalid port: 100000. Must be between 0 and 65535
      */
     public function testPortMustBeValid()
     {
@@ -126,11 +126,11 @@ public function testPortMustBeValid()
 
     /**
      * @expectedException \InvalidArgumentException
-     * @expectedExceptionMessage Invalid port: 0. Must be between 1 and 65535
+     * @expectedExceptionMessage Invalid port: -1. Must be between 0 and 65535
      */
-    public function testWithPortCannotBeZero()
+    public function testWithPortCannotBeNegative()
     {
-        (new Uri())->withPort(0);
+        (new Uri())->withPort(-1);
     }
 
     /**