diff --git a/bilby/core/utils.py b/bilby/core/utils.py
index ef1bec99b20d7c3188af0ec732fe43ef15af4aae..b9a9dba3b6f82c97c39aa8983ee9b51410bc9293 100644
--- a/bilby/core/utils.py
+++ b/bilby/core/utils.py
@@ -785,7 +785,7 @@ class UnsortedInterp2d(interp2d):
 
         """
         unsorted_idxs = np.argsort(np.argsort(x))
-        return interp2d.__call__(self, x, y, dx=dx, dy=dy, assume_sorted=False)[unsorted_idxs, :]
+        return interp2d.__call__(self, x, y, dx=dx, dy=dy, assume_sorted=False)[unsorted_idxs]
 
 
 #  Instantiate the default argument parser at runtime