diff --git a/src/applications/files/storage/PhabricatorFile.php b/src/applications/files/storage/PhabricatorFile.php
--- a/src/applications/files/storage/PhabricatorFile.php
+++ b/src/applications/files/storage/PhabricatorFile.php
@@ -272,8 +272,12 @@
     $file->setByteSize($length);
 
     // NOTE: Once we receive the first chunk, we'll detect its MIME type and
-    // update the parent file. This matters for large media files like video.
-    $file->setMimeType('application/octet-stream');
+    // update the parent file if a MIME type hasn't been provided. This matters
+    // for large media files like video.
+    $mime_type = idx($params, 'mime-type');
+    if (!strlen($mime_type)) {
+      $file->setMimeType('application/octet-stream');
+    }
 
     $chunked_hash = idx($params, 'chunkedHash');
 
diff --git a/src/applications/files/uploadsource/PhabricatorFileUploadSource.php b/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
--- a/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
+++ b/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
@@ -6,6 +6,8 @@
   private $name;
   private $relativeTTL;
   private $viewPolicy;
+  private $mimeType;
+  private $authorPHID;
 
   private $rope;
   private $data;
@@ -51,6 +53,24 @@
     return $this->byteLimit;
   }
 
+  public function setMIMEType($mime_type) {
+    $this->mimeType = $mime_type;
+    return $this;
+  }
+
+  public function getMIMEType() {
+    return $this->mimeType;
+  }
+
+  public function setAuthorPHID($author_phid) {
+    $this->authorPHID = $author_phid;
+    return $this;
+  }
+
+  public function getAuthorPHID() {
+    return $this->authorPHID;
+  }
+
   public function uploadFile() {
     if (!$this->shouldChunkFile()) {
       return $this->writeSingleFile();
@@ -245,6 +265,16 @@
       $parameters['ttl.relative'] = $ttl;
     }
 
+    $mime_type = $this->getMimeType();
+    if ($mime_type !== null) {
+      $parameters['mime-type'] = $mime_type;
+    }
+
+    $author_phid = $this->getAuthorPHID();
+    if ($author_phid !== null) {
+      $parameters['authorPHID'] = $author_phid;
+    }
+
     return $parameters;
   }
 
diff --git a/src/applications/search/controller/PhabricatorApplicationSearchController.php b/src/applications/search/controller/PhabricatorApplicationSearchController.php
--- a/src/applications/search/controller/PhabricatorApplicationSearchController.php
+++ b/src/applications/search/controller/PhabricatorApplicationSearchController.php
@@ -461,15 +461,20 @@
 
         $export_result = $format->newFileData();
 
-        $file = PhabricatorFile::newFromFileData(
-          $export_result,
-          array(
-            'name' => $filename,
-            'authorPHID' => $viewer->getPHID(),
-            'ttl.relative' => phutil_units('15 minutes in seconds'),
-            'viewPolicy' => PhabricatorPolicies::POLICY_NOONE,
-            'mime-type' => $mime_type,
-          ));
+        // We have all the data in one big string and aren't actually
+        // streaming it, but pretending that we are allows us to actviate
+        // the chunk engine and store large files.
+        $iterator = new ArrayIterator(array($export_result));
+
+        $source = id(new PhabricatorIteratorFileUploadSource())
+          ->setName($filename)
+          ->setViewPolicy(PhabricatorPolicies::POLICY_NOONE)
+          ->setMIMEType($mime_type)
+          ->setRelativeTTL(phutil_units('60 minutes in seconds'))
+          ->setAuthorPHID($viewer->getPHID())
+          ->setIterator($iterator);
+
+        $file = $source->uploadFile();
 
         return $this->newDialog()
           ->setTitle(pht('Download Results'))