diff --git a/quaternions.py b/quaternions.py
index 2ad6a5d..b1a6067 100644
--- a/quaternions.py
+++ b/quaternions.py
@@ -61,7 +61,7 @@ def pure_quat(v):
 def quat_inv(q):
     #Note, 'empty_like' is necessary to prevent in-place modification (which is not auto-diff'able)
     if q.dim() < 2:
-        q = q.unsqueeze()
+        q = q.unsqueeze(dim=0)
     q_inv = torch.empty_like(q)
     q_inv[:, :3] = -1*q[:, :3]
     q_inv[:, 3] = q[:, 3]