diff --git a/features/bootstrap/Aws/Test/Integ/MultipartContext.php b/features/bootstrap/Aws/Test/Integ/MultipartContext.php
index 01cbd12..a1f7aa8 100644
--- a/features/bootstrap/Aws/Test/Integ/MultipartContext.php
+++ b/features/bootstrap/Aws/Test/Integ/MultipartContext.php
@@ -38,7 +38,7 @@ class MultipartContext implements Context, SnippetAcceptingContext
      */
     public function iHaveASeekableReadStream()
     {
-        $this->stream = Psr7\stream_for(Psr7\try_fopen(self::$tempFile, 'r'));
+        $this->stream = Psr7\Utils::streamFor(Psr7\Utils::tryFopen(self::$tempFile, 'r'));
     }
 
     /**
diff --git a/features/bootstrap/Aws/Test/Integ/S3Context.php b/features/bootstrap/Aws/Test/Integ/S3Context.php
index ee65f75..eb2ae97 100644
--- a/features/bootstrap/Aws/Test/Integ/S3Context.php
+++ b/features/bootstrap/Aws/Test/Integ/S3Context.php
@@ -148,7 +148,7 @@ public function iSendThePreSignedRequest()
     public function iChangeTheBodyOfThePreSignedRequestToBe($body)
     {
         $this->presignedRequest = $this->presignedRequest
-            ->withBody(Psr7\stream_for($body));
+            ->withBody(Psr7\Utils::streamFor($body));
     }
 
     /**
@@ -157,7 +157,7 @@ public function iChangeTheBodyOfThePreSignedRequestToBe($body)
     public function iHaveAnClientAndIHaveAFile()
     {
         $this->s3Client = self::getSdk()->createS3();
-        $this->stream = Psr7\stream_for(Psr7\try_fopen(self::$tempFile, 'r'));
+        $this->stream = Psr7\Utils::streamFor(Psr7\Utils::tryFopen(self::$tempFile, 'r'));
     }
 
     /**
diff --git a/features/bootstrap/Aws/Test/PerformanceContext.php b/features/bootstrap/Aws/Test/PerformanceContext.php
index 4f0de3a..7cb6734 100644
--- a/features/bootstrap/Aws/Test/PerformanceContext.php
+++ b/features/bootstrap/Aws/Test/PerformanceContext.php
@@ -205,7 +205,7 @@ public function iUploadTheFile()
     public function thenDownloadTheFile()
     {
         $this->addMockResults($this->s3Client, [new Result([
-            'Body' => Psr7\stream_for(Psr7\try_fopen($this->tempFilePath, 'rb')),
+            'Body' => Psr7\Utils::streamFor(Psr7\Utils::tryFopen($this->tempFilePath, 'rb')),
         ])]);
 
         $this->s3Client->getObject([
diff --git a/src/Signature/SignatureV2.php b/src/Signature/SignatureV2.php
index 2712b4b..0df5a30 100644
--- a/src/Signature/SignatureV2.php
+++ b/src/Signature/SignatureV2.php
@@ -15,7 +15,7 @@ public function signRequest(
         RequestInterface $request,
         CredentialsInterface $credentials
     ) {
-        $params = Psr7\parse_query($request->getBody());
+        $params = Psr7\Query::parse($request->getBody());
         $params['Timestamp'] = gmdate('c');
         $params['SignatureVersion'] = '2';
         $params['SignatureMethod'] = 'HmacSHA256';
@@ -40,7 +40,7 @@ public function signRequest(
             )
         );
 
-        return $request->withBody(Psr7\stream_for(http_build_query($params)));
+        return $request->withBody(Psr7\Utils::streamFor(http_build_query($params)));
     }
 
     public function presign(
diff --git a/tests/Signature/SignatureV2Test.php b/tests/Signature/SignatureV2Test.php
index 415ee8a..2cd5598 100644
--- a/tests/Signature/SignatureV2Test.php
+++ b/tests/Signature/SignatureV2Test.php
@@ -32,7 +32,7 @@ public function testSignsRequestsWithSecurityToken()
             . "Host: foo.com\r\n"
             . "Content-Type: application/x-www-form-urlencoded\r\n\r\n"
             . "Test=123&Other=456&Timestamp=Fri%2C+09+Sep+2011+23%3A36%3A00+GMT&SignatureVersion=2&SignatureMethod=HmacSHA256&AWSAccessKeyId=AKIDEXAMPLE&SecurityToken=foo&Signature=NzQ9b5Kx6qlKj2UIK6QHIrmq5ypogh9PhBHVXKA4RU4%3D";
-        $this->assertEquals($expected, Psr7\str($result));
+        $this->assertEquals($expected, Psr7\Message::toString($result));
     }
 
     public function testCanSignBodyWithStructureShapes()
@@ -52,7 +52,7 @@ public function testCanSignBodyWithStructureShapes()
             . "Host: foo.com\r\n"
             . "Content-Type: application/x-www-form-urlencoded\r\n\r\n"
             . "Test=123&Other=456&Nested.1.Name=foo&Nested.1.Value=bar&Timestamp=Fri%2C+09+Sep+2011+23%3A36%3A00+GMT&SignatureVersion=2&SignatureMethod=HmacSHA256&AWSAccessKeyId=AKIDEXAMPLE&SecurityToken=foo&Signature=MbXBpe7leHe6O49B0CU86h%2By0GKFfQ9rBVCNvQWQlB0%3D";
-        $this->assertEquals($expected, Psr7\str($result));
+        $this->assertEquals($expected, Psr7\Message::toString($result));
     }
 
     /**