diff --git a/backend/services/falukantService.js b/backend/services/falukantService.js
index 0b159b2..d564be2 100644
--- a/backend/services/falukantService.js
+++ b/backend/services/falukantService.js
@@ -194,6 +194,12 @@ async function calcRegionalSellPrice(product, knowledgeFactor, regionId, worthPe
         if (hasChancellor) return 0;
 
         // Now compute cumulative tax but exclude regions whose regionType.labelTr is in exemptTypes
+        // Konvertiere exemptTypes Set zu einem PostgreSQL-Array-String
+        const exemptTypesArray = Array.from(exemptTypes);
+        const exemptTypesString = exemptTypesArray.length > 0 
+            ? `ARRAY[${exemptTypesArray.map(t => `'${t.replace(/'/g, "''")}'`).join(',')}]`
+            : `ARRAY[]::text[]`;
+        
         const rows = await sequelize.query(
             `WITH RECURSIVE ancestors AS (
                 SELECT r.id, r.parent_id, r.tax_percent, rt.label_tr as region_type
@@ -206,9 +212,9 @@ async function calcRegionalSellPrice(product, knowledgeFactor, regionId, worthPe
                 JOIN falukant_type.region_type rt2 ON rt2.id = reg.region_type_id
                 JOIN ancestors a ON reg.id = a.parent_id
             )
-            SELECT COALESCE(SUM(CASE WHEN :exempt_types::text[] && ARRAY[region_type] THEN 0 ELSE tax_percent END),0) AS total FROM ancestors;`,
+            SELECT COALESCE(SUM(CASE WHEN ${exemptTypesString} && ARRAY[region_type] THEN 0 ELSE tax_percent END),0) AS total FROM ancestors;`,
             {
-                replacements: { id: regionId, exempt_types: Array.from(exemptTypes) },
+                replacements: { id: regionId },
                 type: sequelize.QueryTypes.SELECT
             }
         );