diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
index 16052ba1..7dee3e0a 100644
--- a/.github/workflows/unit-tests.yml
+++ b/.github/workflows/unit-tests.yml
@@ -2,7 +2,7 @@
 name: Run Unit Tests
 on:
   pull_request:
-    branches: [main]
+    branches: [main, 1.0-dev]
 permissions:
   contents: read
 jobs:
diff --git a/src/a2a/server/tasks/database_task_store.py b/src/a2a/server/tasks/database_task_store.py
index 2ec02831..1605c601 100644
--- a/src/a2a/server/tasks/database_task_store.py
+++ b/src/a2a/server/tasks/database_task_store.py
@@ -189,8 +189,10 @@ async def list(
             count_stmt = select(func.count()).select_from(base_stmt.alias())
             total_count = (await session.execute(count_stmt)).scalar_one()
 
+            # Use coalesce to treat NULL timestamps as empty strings,
+            # which sort last in descending order
             stmt = base_stmt.order_by(
-                timestamp_col.desc().nulls_last(),
+                func.coalesce(timestamp_col, '').desc(),
                 self.task_model.id.desc(),
             )