diff --git a/backend/src/api/bitcoin/bitcoin-api.ts b/backend/src/api/bitcoin/bitcoin-api.ts
index e6d74ddf0..e4557b65f 100644
--- a/backend/src/api/bitcoin/bitcoin-api.ts
+++ b/backend/src/api/bitcoin/bitcoin-api.ts
@@ -216,7 +216,7 @@ class BitcoinApi implements AbstractBitcoinApi {
     if (map[outputType]) {
       return map[outputType];
     } else {
-      return '';
+      return 'unknown';
     }
   }