diff --git a/src/MIME/MimeHeader.php b/src/MIME/MimeHeader.php
index 4ea239b..70f2738 100644
--- a/src/MIME/MimeHeader.php
+++ b/src/MIME/MimeHeader.php
@@ -183,6 +183,7 @@ class MimeHeader {
       // Encode non-7bit body. If body is 7bit, mimeHeaderEncode() does nothing.
       $body = static::mimeHeaderEncode($field['body'], strlen($field['name']));
       $encoded = $body != $field['body'];
+
       $field_string = "{$field['name']}: $body";
       // Fold to match 78 char length limit, and append. The encoding includes
       // folding, so only do it for unencoded body. The \h matches whitespace
@@ -191,7 +192,6 @@ class MimeHeader {
       $field_string = !$encoded ? preg_replace('/(.{0,78})(\h|$)/', "\\1\n\\2", $field_string) : $field_string;
       $header[] = trim($field_string);
     }
-
     return implode("\n", $header);
   }
 
diff --git a/tests/src/Kernel/ModeratorForwardTest.php b/tests/src/Kernel/ModeratorForwardTest.php
index 39028a5..d5e8414 100644
--- a/tests/src/Kernel/ModeratorForwardTest.php
+++ b/tests/src/Kernel/ModeratorForwardTest.php
@@ -172,7 +172,7 @@ class ModeratorForwardTest extends KernelTestBase {
     // Extract the time from original message and append it.
     $received_header = "Received: by localhost via inmail with test_fetcher " . $deliverer->id() . " id <CAFZOsfMjtXehXPGxbiLjydzCY0gCkdngokeQACWQOw+9W5drqQ@mail.gmail.com>;" . substr($forward['received'], strpos($forward['received'], ';')+1) . "\n";
     // Wrap the received header to 78 characters.
-    $expected_headers = $forward_header . $received_header . $expected_headers;
+    $expected_headers =  $forward_header . wordwrap($received_header, 78, "\n ") . $expected_headers;
     // Wrap to 78 characters to match original message.
     $this->assertEqual($forward['raw_headers']->toString(), $expected_headers, 'Forwarded message headers have the correct changes.');
 
diff --git a/tests/src/Unit/MIME/MimeDSNEntityTest.php b/tests/src/Unit/MIME/MimeDSNEntityTest.php
index 582bb49..403a3ee 100644
--- a/tests/src/Unit/MIME/MimeDSNEntityTest.php
+++ b/tests/src/Unit/MIME/MimeDSNEntityTest.php
@@ -93,7 +93,9 @@ class MimeDSNEntityTest extends UnitTestCase {
   protected static function getMessageHeader() {
     return new MimeHeader([
       ['name' => 'Content-type', 'body' => 'multipart/report; report-type=delivery-status; boundary="boundary"'],
-    ]);
+    ],
+      'Content-type: multipart/report; report-type=delivery-status; boundary="boundary"'
+    );
   }
 
   /**
@@ -159,7 +161,9 @@ Subject: My very urgent message
   protected static function getStatusPartHeader() {
     return new MimeHeader([
       ['name' => 'Content-Type', 'body' => 'message/delivery-status'],
-    ]);
+    ],
+      'Content-Type: message/delivery-status'
+    );
   }
 
   /**
@@ -185,7 +189,9 @@ Subject: My very urgent message
   protected static function getPerMessageFields() {
     return new MimeHeader([
       ['name' => 'Reporting-MTA', 'body' => 'dns; example.com'],
-    ]);
+    ],
+      'Reporting-MTA: dns; example.com'
+    );
   }
 
   /**
@@ -196,7 +202,9 @@ Subject: My very urgent message
       ['name' => 'Final-Recipient', 'body' => 'rfc822; user@example.org'],
       ['name' => 'Action', 'body' => 'failed'],
       ['name' => 'Status', 'body' => '5.0.0'],
-    ]);
+    ],
+      "Final-Recipient: rfc822; user@example.org\nAction: failed\nStatus: 5.0.0"
+    );
   }
 
   /**
@@ -212,7 +220,9 @@ Subject: My very urgent message
   protected static function getOriginalPartHeader() {
     return new MimeHeader([
       ['name' => 'Content-Type', 'body' => 'message/rfc822'],
-    ]);
+    ],
+      'Content-Type: message/rfc822'
+    );
   }
 
   /**
diff --git a/tests/src/Unit/MIME/MimeMultipartEntityTest.php b/tests/src/Unit/MIME/MimeMultipartEntityTest.php
index 8507bdc..0c03f93 100644
--- a/tests/src/Unit/MIME/MimeMultipartEntityTest.php
+++ b/tests/src/Unit/MIME/MimeMultipartEntityTest.php
@@ -132,7 +132,11 @@ class MimeMultipartEntityTest extends UnitTestCase {
       ['name' => 'Subject', 'body' => 'Sample message'],
       ['name' => 'MIME-Version', 'body' => '1.0'],
       ['name' => 'Content-type', 'body' => 'multipart/mixed; boundary="simple boundary"'],
-    ]);
+    ],
+      "From: Nathaniel Borenstein <nsb@bellcore.com>\nTo: Ned Freed <ned@innosoft.com>\n" .
+      "Date: Sun, 21 Mar 1993 23:56:48 -0800 (PST)\nSubject: Sample message\n" .
+      "MIME-Version: 1.0\nContent-type: multipart/mixed; boundary=\"simple boundary\""
+  );
   }
 
   /**
@@ -179,7 +183,9 @@ This is the epilogue.  It is also to be ignored.
   protected static function getSecondPartHeader() {
     return new MimeHeader([
       ['name' => 'Content-type', 'body' => 'text/plain; charset=us-ascii'],
-    ]);
+    ],
+      'Content-type: text/plain; charset=us-ascii'
+    );
   }
 
   /**