diff --git a/lightspark/src/client.rs b/lightspark/src/client.rs
index 559ebd9..8f81ebc 100644
--- a/lightspark/src/client.rs
+++ b/lightspark/src/client.rs
@@ -993,7 +993,7 @@ impl<K: OperationSigningKey> LightsparkClient<K> {
             $timeout_secs: Int!
             $maximum_fees_msats: Long!
             $amount_msats: Long
-            $sender_hash: String = null
+            $sender_hash: String
         ) {{
             pay_uma_invoice(input: {{
                 node_id: $node_id