diff --git a/bigchaindb/common/schema/transaction_v2.0.yaml b/bigchaindb/common/schema/transaction_v2.0.yaml
index 0a22b810..913a3cf5 100644
--- a/bigchaindb/common/schema/transaction_v2.0.yaml
+++ b/bigchaindb/common/schema/transaction_v2.0.yaml
@@ -79,7 +79,7 @@ definitions:
     properties:
       amount:
         type: string
-        pattern: "^[0-9]{1,20}$"
+        pattern: "^[1-9][0-9]{0,19}$"
       condition:
         type: object
         additionalProperties: false