diff --git a/src/Forms/GridFieldQueuedExportButton.php b/src/Forms/GridFieldQueuedExportButton.php
index 145d4f1..907256f 100644
--- a/src/Forms/GridFieldQueuedExportButton.php
+++ b/src/Forms/GridFieldQueuedExportButton.php
@@ -195,7 +195,7 @@ public function checkExport($gridField, $request = null)
         ]);
 
         if ($job->JobStatus == QueuedJob::STATUS_COMPLETE) {
-            if (file_exists($this->getExportPath($id))) {
+            if (file_exists($this->getExportPath($id) ?? '')) {
                 $data->DownloadLink = $gridField->Link('/export_download/' . $job->Signature);
             } else {
                 $data->ErrorMessage = _t(
@@ -253,10 +253,10 @@ public function downloadExport($gridField, $request = null)
         $servedName = "export-$now.csv";
 
         $path = $this->getExportPath($id);
-        $content = file_get_contents($path);
+        $content = file_get_contents($path ?? '');
 
-        unlink($path);
-        rmdir(dirname($path));
+        unlink($path ?? '');
+        rmdir(dirname($path ?? ''));
 
         $response = HTTPRequest::send_file($content, $servedName, 'text/csv');
         $response->addHeader('Set-Cookie', 'downloaded_' . $id . '=true; Path=/');
diff --git a/src/Jobs/GenerateCSVJob.php b/src/Jobs/GenerateCSVJob.php
index 9cbb9dd..c44aa9d 100644
--- a/src/Jobs/GenerateCSVJob.php
+++ b/src/Jobs/GenerateCSVJob.php
@@ -139,11 +139,11 @@ public function setSession($session)
     {
         // None of the gridfield actions are needed, and they make the stored session bigger, so pull
         // them out.
-        $actionkeys = array_filter(array_keys($session), function ($i) {
-            return strpos($i, 'gf_') === 0;
+        $actionkeys = array_filter(array_keys($session ?? []), function ($i) {
+            return strpos($i ?? '', 'gf_') === 0;
         });
 
-        $session = array_diff_key($session, array_flip($actionkeys));
+        $session = array_diff_key($session ?? [], array_flip($actionkeys ?? []));
 
         // This causes problems with logins
         unset($session['HTTP_USER_AGENT']);
@@ -176,7 +176,7 @@ public function setIncludeHeader($includeHeader)
 
     protected function makeDir($path)
     {
-        if (!is_dir($path)) {
+        if (!is_dir($path ?? '')) {
             // whether to use 'chmod' to override 'mkdir' perms which obey umask
             $ignore_umask = $this->config()->get('ignore_umask');
 
@@ -189,14 +189,14 @@ protected function makeDir($path)
             }
 
             // convert from octal to decimal for mkdir
-            $permission_mode = octdec($permission_mode);
+            $permission_mode = octdec($permission_mode ?? '');
 
             // make dir with perms that obey the executing user's umask
-            mkdir($path, $permission_mode, true);
+            mkdir($path ?? '', $permission_mode ?? 0, true);
 
             // override perms to ignore user's umask?
             if ($ignore_umask) {
-                chmod($path, $permission_mode);
+                chmod($path ?? '', $permission_mode ?? 0);
             }
         }
     }
@@ -234,7 +234,7 @@ protected function getCSVWriter()
                 $csvWriter->addFormatter(function (array $row) {
                     foreach ($row as &$item) {
                         // [SS-2017-007] Sanitise XLS executable column values with a leading tab
-                        if (preg_match('/^[-@=+].*/', $item)) {
+                        if (preg_match('/^[-@=+].*/', $item ?? '')) {
                             $item = "\t" . $item;
                         }
                     }
@@ -284,7 +284,7 @@ protected function getGridField()
         $queryParams = [$actionKey => $actionValue, 'SecurityID' => $token];
 
         // Get the filters and assign to the url as a get parameter
-        if (is_array($this->Filters) && count($this->Filters) > 0) {
+        if (is_array($this->Filters) && count($this->Filters ?? []) > 0) {
             foreach ($this->Filters as $filter => $value) {
                 $queryParams['filters'][$filter] = $value;
             }
@@ -292,7 +292,7 @@ protected function getGridField()
 
         $url = Controller::join_links(
             $this->GridFieldURL,
-            '?' . http_build_query($queryParams)
+            '?' . http_build_query($queryParams ?? [])
         );
 
         // Restore into the current session the user the job is exporting as
@@ -330,7 +330,7 @@ protected function outputHeader($gridField, $columns)
         // determine the CSV headers. If a field is callable (e.g. anonymous function) then use the
         // source name as the header instead
         foreach ($columns as $columnSource => $columnHeader) {
-            if (is_array($columnHeader) && array_key_exists('title', $columnHeader)) {
+            if (is_array($columnHeader) && array_key_exists('title', $columnHeader ?? [])) {
                 $headers[] = $columnHeader['title'];
             } else {
                 $headers[] = (!is_string($columnHeader) && is_callable($columnHeader)) ? $columnSource : $columnHeader;
@@ -447,7 +447,7 @@ public function process()
             // Check to see if we need to wait for some time for asset synchronisation to complete
             $sleepTime = (int) $this->config()->get('sync_sleep_seconds');
             if ($sleepTime > 0) {
-                sleep($sleepTime);
+                sleep($sleepTime ?? 0);
             }
 
             $this->isComplete = true;
diff --git a/tests/GenerateCSVJobTest.php b/tests/GenerateCSVJobTest.php
index c5dd060..35f9329 100644
--- a/tests/GenerateCSVJobTest.php
+++ b/tests/GenerateCSVJobTest.php
@@ -35,7 +35,7 @@ protected function setUp(): void
     protected function tearDown(): void
     {
         foreach ($this->paths as $path) {
-            Filesystem::removeFolder(dirname($path));
+            Filesystem::removeFolder(dirname($path ?? ''));
         }
         parent::tearDown();
     }
@@ -70,9 +70,9 @@ public function testGenerateExport()
             '"Record 3","<p>""Record 3"" Body</p>","2015-01-03 23:34:01"',
             '',
         ];
-        $actual = file_get_contents($path);
+        $actual = file_get_contents($path ?? '');
         // Note: strtolower() is for case insensitive comparison, since field label casing changed in SS 4.3
-        $this->assertStringContainsString('title,content,"publish on"', strtolower($actual));
+        $this->assertStringContainsString('title,content,"publish on"', strtolower($actual ?? ''));
         $this->assertStringContainsString(implode("\r\n", $expected), $actual);
     }
 
@@ -118,9 +118,9 @@ public function testGenerateExportOverMultipleSteps()
             '"Record 3","<p>""Record 3"" Body</p>","2015-01-03 23:34:01"',
             '',
         ];
-        $actual = file_get_contents($path);
+        $actual = file_get_contents($path ?? '');
         // Note: strtolower() is for case insensitive comparison, since field label casing changed in SS 4.3
-        $this->assertStringContainsString('title,content,"publish on"', strtolower($actual));
+        $this->assertStringContainsString('title,content,"publish on"', strtolower($actual ?? ''));
         $this->assertStringContainsString(implode("\r\n", $expected), $actual);
     }