diff --git a/app/Http/Api/Filter/Filter.php b/app/Http/Api/Filter/Filter.php
index 3faefb95d..2072c2040 100644
--- a/app/Http/Api/Filter/Filter.php
+++ b/app/Http/Api/Filter/Filter.php
@@ -155,12 +155,12 @@ public function format(
 
         if ($comparisonOperator !== null) {
             $formattedFilter = $formattedFilter->append(Criteria::PARAM_SEPARATOR)
-                ->append($comparisonOperator->value);
+                ->append(strtolower($comparisonOperator->name));
         }
 
         if ($logicalOperator !== null) {
             $formattedFilter = $formattedFilter->append(Criteria::PARAM_SEPARATOR)
-                ->append($logicalOperator->value);
+                ->append(strtolower($logicalOperator->name));
         }
 
         return $formattedFilter->lower()->__toString();