diff --git a/brie/brie_org.py b/brie/brie_org.py
index a1e0e95..5949839 100644
--- a/brie/brie_org.py
+++ b/brie/brie_org.py
@@ -1230,11 +1230,12 @@ def update(self):
                 ] = len(
                     self._inlet_idx
                 )  # number of inlets
-                self._inlet_migr[
-                    np.fix(self._time_index / self._dtsave).astype(int) - 1
-                ] = np.mean(migr_up / self._dt)
 
                 if len(self._inlet_idx) != 0:
+                    self._inlet_migr[
+                        np.fix(self._time_index / self._dtsave).astype(int) - 1
+                        ] = np.mean(migr_up / self._dt)
+
                     self._inlet_Qs_in[
                         np.fix(self._time_index / self._dtsave).astype(int) - 1
                     ] = np.mean(Qs_in)