diff --git a/src/CwpSearchResult.php b/src/CwpSearchResult.php
index bd42c79..19d9540 100644
--- a/src/CwpSearchResult.php
+++ b/src/CwpSearchResult.php
@@ -200,9 +200,9 @@ protected function getLink($terms, $format = null)
         if (!$terms) {
             return null;
         }
-        $link = 'search/SearchForm?Search='.rawurlencode($terms);
+        $link = 'search/SearchForm?Search='.rawurlencode($terms ?? '');
         if ($format) {
-            $link .= '&format='.rawurlencode($format);
+            $link .= '&format='.rawurlencode($format ?? '');
         }
         return $link;
     }
@@ -210,6 +210,6 @@ protected function getLink($terms, $format = null)
     public function hasField($field)
     {
         // Fix customise not detecting custom field getters
-        return array_key_exists($field, $this->config()->casting);
+        return array_key_exists($field, $this->config()->casting ?? []);
     }
 }
diff --git a/src/Extensions/SynonymValidator.php b/src/Extensions/SynonymValidator.php
index af5d35b..ca0511c 100644
--- a/src/Extensions/SynonymValidator.php
+++ b/src/Extensions/SynonymValidator.php
@@ -71,12 +71,12 @@ protected function validateValue($value)
     {
         // strip empty lines
         $lines = array_filter(
-            explode("\n", $value)
+            explode("\n", $value ?? '')
         );
 
         // strip comments (lines beginning with "#")
-        $lines = array_filter($lines, function ($line) {
-            $line = trim($line);
+        $lines = array_filter($lines ?? [], function ($line) {
+            $line = trim($line ?? '');
 
             return !empty($line) && $line[0] !== '#';
         });
@@ -100,10 +100,10 @@ protected function validateValue($value)
      */
     protected function validateLine($line)
     {
-        $line = trim($line);
+        $line = trim($line ?? '');
 
-        $parts = explode(',', $line);
-        $parts = array_filter($parts);
+        $parts = explode(',', $line ?? '');
+        $parts = array_filter($parts ?? []);
 
         foreach ($parts as $part) {
             if (!$this->validatePart($part)) {
@@ -123,9 +123,9 @@ protected function validateLine($line)
      */
     protected function validatePart($part)
     {
-        if (strpos($part, '=>') !== false) {
-            $subs = explode('=>', $part);
-            $subs = array_filter($subs);
+        if (strpos($part ?? '', '=>') !== false) {
+            $subs = explode('=>', $part ?? '');
+            $subs = array_filter($subs ?? []);
 
             foreach ($subs as $sub) {
                 if (!$this->validateNoSpaces($sub)) {
@@ -147,10 +147,10 @@ protected function validatePart($part)
     protected function validateNoSpaces($value)
     {
         // allow spaces at the beginning and end of the value
-        $value = trim($value);
+        $value = trim($value ?? '');
 
         // does the value contain 1 or more whitespace characters?
-        if (preg_match('/\s+/', $value)) {
+        if (preg_match('/\s+/', $value ?? '')) {
             return false;
         }
 
diff --git a/src/Solr/CwpSolr.php b/src/Solr/CwpSolr.php
index bbd8e6d..af0cf31 100644
--- a/src/Solr/CwpSolr.php
+++ b/src/Solr/CwpSolr.php
@@ -60,7 +60,7 @@ public static function configure()
 
         // Allow users to override extras path.
         // CAUTION: CWP does not permit usage of customised solrconfig.xml.
-        if (isset($options['extraspath']) && file_exists($options['extraspath'])) {
+        if (isset($options['extraspath']) && file_exists($options['extraspath'] ?? '')) {
             $solrOptions['extraspath'] = $options['extraspath'];
         } elseif (file_exists(BASE_PATH . '/app/conf/extras')) {
             $solrOptions['extraspath'] = BASE_PATH . '/app/conf/extras';
diff --git a/src/Solr/CwpSolrConfigStore.php b/src/Solr/CwpSolrConfigStore.php
index ae659e7..57d8851 100644
--- a/src/Solr/CwpSolrConfigStore.php
+++ b/src/Solr/CwpSolrConfigStore.php
@@ -46,7 +46,7 @@ public function __construct($config)
      */
     public function uploadFile($index, $file)
     {
-        $this->uploadString($index, basename($file), file_get_contents($file));
+        $this->uploadString($index, basename($file ?? ''), file_get_contents($file ?? ''));
     }
 
     /**