diff --git a/src/cditools/eiger_async.py b/src/cditools/eiger_async.py
index ec14bcb6..af58b722 100644
--- a/src/cditools/eiger_async.py
+++ b/src/cditools/eiger_async.py
@@ -40,6 +40,7 @@
 from ophyd_async.epics.adcore import (
     ADBaseIO,
     ADImageMode,
+    ADState,
     AreaDetector,
     NDFileIO,
     NDPluginBaseIO,
@@ -528,7 +529,8 @@ async def wait_for_idle(self):
 
     # We are intentionally not calling the base class implementation
     async def ensure_ready(self):
-        self._cached_acquire_state = await self.driver.acquire.get_value()
+        detector_state = await self.driver.detector_state.get_value()
+        self._cached_acquire_state = detector_state == ADState.ACQUIRE
         self._cached_trigger_mode = await self.driver.trigger_mode.get_value()
         self._cached_image_mode = await self.driver.image_mode.get_value()