diff --git a/skais/ais/ais_trajectory.py b/skais/ais/ais_trajectory.py
index 7b504a0413a6edae3f1b1f13f635f92eb96417f4..69c96979b866b759b1d673317d101cdbc2231359 100644
--- a/skais/ais/ais_trajectory.py
+++ b/skais/ais/ais_trajectory.py
@@ -24,7 +24,7 @@ def compute_trajectory(times, time_gap):
 
 
 def apply_func_on_window(dat, func, radius, on_edge='copy'):
-    result = np.zeros(dat.shape)
+    result = np.zeros(dat.shape[0])
     if on_edge == 'copy':
         if len(dat.shape) == 1:
             dat = np.concatenate([np.full(radius, dat[0]), dat, np.full(radius, dat[-1])])
@@ -152,4 +152,4 @@ class AISTrajectory(AISPoints):
             work_df = work_df[i:]
             index += i
 
-        return result
\ No newline at end of file
+        return result