diff --git a/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py b/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py
index b50cb06..e2b8718 100644
--- a/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py
+++ b/csaxs_bec/devices/epics/mcs_card/mcs_card_csaxs.py
@@ -169,6 +169,7 @@ class MCSCardCSAXS(PSIDeviceBase, MCSCard):
         )
         self._current_data_index: int = 0
         self._mca_counter_index: int = 0
+        self._num_lines: int = 1
         self._current_data: dict[str, dict[Literal["value", "timestamp"], list[int] | float]] = {}
         self._omit_mca_callbacks: threading.Event = threading.Event()
         self.scan_parameters: ScanServerScanInfo | None = None