diff --git a/faststream_outbox/schema_validation.py b/faststream_outbox/schema_validation.py
index 93a2588..055d734 100644
--- a/faststream_outbox/schema_validation.py
+++ b/faststream_outbox/schema_validation.py
@@ -230,6 +230,9 @@ def _validate_check_constraints_sync(connection: "Connection", table: "Table") -
 )
 
 
+_PENDING_IDX_UPGRADE_URL = "https://faststream-outbox.modern-python.org/operations/alembic/#upgrading-to-015"
+
+
 def _compose_schema_mismatch_message(errors: list[str], *, has_blind_drift: bool) -> str:
     """Build the validate_schema RuntimeError text; append the remediation pointer for Alembic-blind drift."""
     msg = _SCHEMA_MISMATCH_PREFIX + "; ".join(errors)
@@ -377,5 +380,8 @@ def _drift_entry_to_error(entry: "tuple[typing.Any, ...]", table_name: str) -> s
     if op == "add_index":
         idx = entry[1]
         cols = [c.name for c in idx.columns]
-        return f"table '{table_name}' missing index over {cols} (name={idx.name!r}, unique={bool(idx.unique)})"
+        error = f"table '{table_name}' missing index over {cols} (name={idx.name!r}, unique={bool(idx.unique)})"
+        if idx.name.endswith(_PENDING_IDX_SUFFIX):
+            error += f"; a table created before 0.15 needs this index rebuilt: {_PENDING_IDX_UPGRADE_URL}"
+        return error
     return None
diff --git a/tests/test_integration.py b/tests/test_integration.py
index 35a8ed8..0f99b0a 100644
--- a/tests/test_integration.py
+++ b/tests/test_integration.py
@@ -115,7 +115,7 @@ async def test_validate_schema_reports_the_pre_0_15_pending_index_shape(
             text(f'CREATE INDEX "{idx}" ON {outbox_table.name} (queue, next_attempt_at) WHERE acquired_token IS NULL'),
         )
     client = OutboxClient(pg_engine, outbox_table)
-    with pytest.raises(RuntimeError, match="pending_idx"):
+    with pytest.raises(RuntimeError, match=r"pending_idx.*operations/alembic/#upgrading-to-015"):
         await client.validate_schema()