--- a/src/main/java/org/qortal/controller/arbitrary/ArbitraryDataCacheManager.java
+++ b/src/main/java/org/qortal/controller/arbitrary/ArbitraryDataCacheManager.java
@@ -146,7 +146,11 @@
                         preparedStatement.addBatch();
                     }
 
-                    preparedStatement.executeBatch();
+                    // HSQLDB rejects executeBatch when no addBatch occurred.
+                    // Empty fresh databases still need the normal completion flag.
+                    if (!signatureByData.isEmpty()) {
+                        preparedStatement.executeBatch();
+                    }
 
                     LOGGER.info("Updated arbitrary resources with latest signatures");