diff --git a/src/calng/DetectorAssembler.py b/src/calng/DetectorAssembler.py
index 745d6e5486dec830669cbb0a740e6e700912c5a4..0ebb37826cfcc5db2285e6beaccdaa752f32e7f7 100644
--- a/src/calng/DetectorAssembler.py
+++ b/src/calng/DetectorAssembler.py
@@ -58,6 +58,7 @@ def module_index_schema():
         .reconfigurable()
         .commit(),
     )
+    return schema
 
 
 @KARABO_CLASSINFO("DetectorAssembler", deviceVersion)
@@ -89,7 +90,6 @@ class DetectorAssembler(TrainMatcher.TrainMatcher):
             .metricPrefix(MetricPrefix.MILLI)
             .readOnly()
             .initialValue(0)
-            .needsAcknowledging(False)
             .commit(),
 
             STRING_ELEMENT(expected)