diff --git a/src/Filter/MapClassificationsFilter.php b/src/Filter/MapClassificationsFilter.php
index 229b492..af5d467 100644
--- a/src/Filter/MapClassificationsFilter.php
+++ b/src/Filter/MapClassificationsFilter.php
@@ -92,7 +92,7 @@ private function filterClassification(array $values, array $map): array
     {
         $mappedValues = [];
         foreach ($values as $item) {
-            $mapped = $map[strtolower($item)] ?? false;
+            $mapped = $map[strtolower(trim($item))] ?? false;
             if ($mapped === false) {
                 $mappedValues[] = $item;
                 continue;