diff --git a/laborious/activities/model_metrics.py b/laborious/activities/model_metrics.py
index 3d55997..ae0f231 100644
--- a/laborious/activities/model_metrics.py
+++ b/laborious/activities/model_metrics.py
@@ -293,7 +293,7 @@ class ModelMetrics(SientiaMonitoring):
         metrics = input_data['metrics']
         interval_minutes = input_data['interval_minutes']
 
-        data_size = data.shape[0]
+        data_size = target_data.shape[0]
 
         output_data = []