diff --git a/src/Form/SentencesSearchForm.php b/src/Form/SentencesSearchForm.php
index 79d3da66b6..524120100b 100644
--- a/src/Form/SentencesSearchForm.php
+++ b/src/Form/SentencesSearchForm.php
@@ -186,7 +186,10 @@ protected function setDataTags(string $tags) {
             $appliedTags = $this->search->filterByTags($tagsArray);
             $tags = implode(',', $appliedTags);
 
-            $ignoredTags = array_diff($tagsArray, $appliedTags);
+            $ignoredTags = array_diff(
+                    array_reduce($tagsArray, function($carry,$item){$carry[] = strtolower($item); return $carry; },[]), 
+                    array_reduce($appliedTags, function($carry,$item){$carry[] = strtolower($item); return $carry; },[]), 
+                );
             foreach ($ignoredTags as $tagName) {
                 $this->ignored[] = format(
                     /* @translators: This string will be preceded by