diff --git a/eddymotion/model.py b/eddymotion/model.py
index 9ce83233..a22ce278 100644
--- a/eddymotion/model.py
+++ b/eddymotion/model.py
@@ -94,15 +94,15 @@ def predict(self, gradient, **kwargs):
 class AverageDWModel:
     """A trivial model that returns an average map."""
 
-    __slots__ = ("_data",)
+    __slots__ = ("_data", "_gtab")
 
     def __init__(self, gtab, **kwargs):
         """Implement object initialization."""
-        return  # do nothing at initialization time
+        self._gtab = gtab
 
     def fit(self, data, **kwargs):
         """Calculate the average."""
-        self._data = data.mean(-1)
+        self._data = data[..., self._gtab[..., 3] > 50].mean(-1)
 
     def predict(self, gradient, **kwargs):
         """Return the average map."""