diff --git a/src/Message/Response.php b/src/Message/Response.php
index d0bc04c..1e1a1e3 100644
--- a/src/Message/Response.php
+++ b/src/Message/Response.php
@@ -62,17 +62,17 @@ class Response extends Message implements ResponseInterface
      * @link http://tools.ietf.org/html/rfc7231#section-6
      * @link http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
      * @param integer $code The 3-digit integer result code to set.
-     * @param null|string $reasonPhrase The reason phrase to use with the
+     * @param string $reasonPhrase The reason phrase to use with the
      *     provided status code; if none is provided, implementations MAY
      *     use the defaults as suggested in the HTTP specification.
      * @return self
      * @throws \InvalidArgumentException For invalid status code arguments.
      */
-    public function withStatus($code, $reasonPhrase = null)
+    public function withStatus($code, $reasonPhrase = "")
     {
         $response = clone $this;
         $response->statusCode = $code;
-        if ($reasonPhrase === null) {
+        if (!$reasonPhrase) {
             $reasonPhrase = $this->getDefaultReasonPhraseForStatusCode($code);
         }
         $response->reasonPhrase = $reasonPhrase;
@@ -103,69 +103,66 @@ class Response extends Message implements ResponseInterface
      */
     private function getDefaultReasonPhraseForStatusCode($statusCode)
     {
-        static $reasonPhraseLookup = null;
-        if ($reasonPhraseLookup === null) {
-            $reasonPhraseLookup = [
-                100 => "Continue",
-                101 => "Switching Protocols",
-                102 => "Processing",
-                200 => "OK",
-                201 => "Created",
-                202 => "Accepted",
-                203 => "Non-Authoritative Information",
-                204 => "No Content",
-                205 => "Reset Content",
-                206 => "Partial Content",
-                207 => "Multi-Status",
-                208 => "Already Reported",
-                226 => "IM Used",
-                300 => "Multiple Choices",
-                301 => "Moved Permanently",
-                302 => "Found",
-                303 => "See Other",
-                304 => "Not Modified",
-                305 => "Use Proxy",
-                307 => "Temporary Redirect",
-                308 => "Permanent Redirect",
-                400 => "Bad Request",
-                401 => "Unauthorized",
-                402 => "Payment Required",
-                403 => "Forbidden",
-                404 => "Not Found",
-                405 => "Method Not Allowed",
-                406 => "Not Acceptable",
-                407 => "Proxy Authentication Required",
-                408 => "Request Timeout",
-                409 => "Conflict",
-                410 => "Gone",
-                411 => "Length Required",
-                412 => "Precondition Failed",
-                413 => "Payload Too Large",
-                414 => "URI Too Long",
-                415 => "Unsupported Media Type",
-                416 => "Range Not Satisfiable",
-                417 => "Expectation Failed",
-                421 => "Misdirected Request",
-                422 => "Unprocessable Entity",
-                423 => "Locked",
-                424 => "Failed Dependency",
-                426 => "Upgrade Required",
-                428 => "Precondition Required",
-                429 => "Too Many Requests",
-                431 => "Request Header Fields Too Large",
-                500 => "Internal Server Error",
-                501 => "Not Implemented",
-                502 => "Bad Gateway",
-                503 => "Service Unavailable",
-                504 => "Gateway Timeout",
-                505 => "HTTP Version Not Supported",
-                506 => "Variant Also Negotiates",
-                507 => "Insufficient Storage",
-                508 => "Loop Detected",
-                510 => "Not Extended",
-                511 => "Network Authentication Required"
-            ];
-        }
+        $reasonPhraseLookup = [
+            100 => "Continue",
+            101 => "Switching Protocols",
+            102 => "Processing",
+            200 => "OK",
+            201 => "Created",
+            202 => "Accepted",
+            203 => "Non-Authoritative Information",
+            204 => "No Content",
+            205 => "Reset Content",
+            206 => "Partial Content",
+            207 => "Multi-Status",
+            208 => "Already Reported",
+            226 => "IM Used",
+            300 => "Multiple Choices",
+            301 => "Moved Permanently",
+            302 => "Found",
+            303 => "See Other",
+            304 => "Not Modified",
+            305 => "Use Proxy",
+            307 => "Temporary Redirect",
+            308 => "Permanent Redirect",
+            400 => "Bad Request",
+            401 => "Unauthorized",
+            402 => "Payment Required",
+            403 => "Forbidden",
+            404 => "Not Found",
+            405 => "Method Not Allowed",
+            406 => "Not Acceptable",
+            407 => "Proxy Authentication Required",
+            408 => "Request Timeout",
+            409 => "Conflict",
+            410 => "Gone",
+            411 => "Length Required",
+            412 => "Precondition Failed",
+            413 => "Payload Too Large",
+            414 => "URI Too Long",
+            415 => "Unsupported Media Type",
+            416 => "Range Not Satisfiable",
+            417 => "Expectation Failed",
+            421 => "Misdirected Request",
+            422 => "Unprocessable Entity",
+            423 => "Locked",
+            424 => "Failed Dependency",
+            426 => "Upgrade Required",
+            428 => "Precondition Required",
+            429 => "Too Many Requests",
+            431 => "Request Header Fields Too Large",
+            500 => "Internal Server Error",
+            501 => "Not Implemented",
+            502 => "Bad Gateway",
+            503 => "Service Unavailable",
+            504 => "Gateway Timeout",
+            505 => "HTTP Version Not Supported",
+            506 => "Variant Also Negotiates",
+            507 => "Insufficient Storage",
+            508 => "Loop Detected",
+            510 => "Not Extended",
+            511 => "Network Authentication Required"
+        ];
         if (isset($reasonPhraseLookup[$statusCode])) {
             return $reasonPhraseLookup[$statusCode];
         }
diff --git a/src/Message/Stream.php b/src/Message/Stream.php
index b0429ff..4e6a428 100644
--- a/src/Message/Stream.php
+++ b/src/Message/Stream.php
@@ -49,8 +49,14 @@ class Stream implements StreamInterface
      */
     public function __toString()
     {
-        rewind($this->resource);
-        return $this->getContents();
+        $string = "";
+        try {
+            rewind($this->resource);
+            $string = $this->getContents();
+        } catch (Exception $e) {
+            // Silence exceptions in order to conform with PHP's string casting operations.
+        }
+        return $string;
     }
 
     /**
diff --git a/test/tests/unit/Message/ResponseTest.php b/test/tests/unit/Message/ResponseTest.php
index c4344eb..e1295e1 100644
--- a/test/tests/unit/Message/ResponseTest.php
+++ b/test/tests/unit/Message/ResponseTest.php
@@ -76,7 +76,7 @@ class ResponseTest extends \PHPUnit_Framework_TestCase
             [503, null, "Service Unavailable"],
             [504, null, "Gateway Timeout"],
             [505, null, "HTTP Version Not Supported"],
-            [598, null, null],
+            [598, null, ""],
             [599, "Nonstandard", "Nonstandard"]
         ];
     }