diff --git a/api/server.js b/api/server.js
index 0afbaea..b7ff4ec 100644
--- a/api/server.js
+++ b/api/server.js
@@ -154,24 +154,43 @@ app.post('/api/filaments', authenticateToken, async (req, res) => {
 app.put('/api/filaments/:id', authenticateToken, async (req, res) => {
   const { id } = req.params;
   const { tip, finish, boja, boja_hex, refill, spulna, cena, sale_percentage, sale_active, sale_start_date, sale_end_date } = req.body;
-  
+
   try {
     // Ensure refill and spulna are numbers
     const refillNum = parseInt(refill) || 0;
     const spulnaNum = parseInt(spulna) || 0;
     const kolicina = refillNum + spulnaNum;
-    
-    const result = await pool.query(
-      `UPDATE filaments 
-       SET tip = $1, finish = $2, boja = $3, boja_hex = $4, 
-           refill = $5, spulna = $6, kolicina = $7, cena = $8,
-           sale_percentage = $9, sale_active = $10, 
-           sale_start_date = $11, sale_end_date = $12,
-           updated_at = CURRENT_TIMESTAMP
-       WHERE id = $13 RETURNING *`,
-      [tip, finish, boja, boja_hex, refillNum, spulnaNum, kolicina, cena, 
-       sale_percentage || 0, sale_active || false, sale_start_date, sale_end_date, id]
-    );
+
+    // Check if sale fields are provided in the request
+    const hasSaleFields = 'sale_percentage' in req.body || 'sale_active' in req.body ||
+                          'sale_start_date' in req.body || 'sale_end_date' in req.body;
+
+    let result;
+    if (hasSaleFields) {
+      // Update with sale fields if they are provided
+      result = await pool.query(
+        `UPDATE filaments
+         SET tip = $1, finish = $2, boja = $3, boja_hex = $4,
+             refill = $5, spulna = $6, kolicina = $7, cena = $8,
+             sale_percentage = $9, sale_active = $10,
+             sale_start_date = $11, sale_end_date = $12,
+             updated_at = CURRENT_TIMESTAMP
+         WHERE id = $13 RETURNING *`,
+        [tip, finish, boja, boja_hex, refillNum, spulnaNum, kolicina, cena,
+         sale_percentage || 0, sale_active || false, sale_start_date, sale_end_date, id]
+      );
+    } else {
+      // Update without touching sale fields if they are not provided
+      result = await pool.query(
+        `UPDATE filaments
+         SET tip = $1, finish = $2, boja = $3, boja_hex = $4,
+             refill = $5, spulna = $6, kolicina = $7, cena = $8,
+             updated_at = CURRENT_TIMESTAMP
+         WHERE id = $9 RETURNING *`,
+        [tip, finish, boja, boja_hex, refillNum, spulnaNum, kolicina, cena, id]
+      );
+    }
+
     res.json(result.rows[0]);
   } catch (error) {
     console.error('Error updating filament:', error);