diff --git a/liegroups/numpy/so3.py b/liegroups/numpy/so3.py
index aff0512..e4ecc41 100644
--- a/liegroups/numpy/so3.py
+++ b/liegroups/numpy/so3.py
@@ -78,9 +78,9 @@ def from_quaternion(cls, quat, ordering='wxyz'):
         if not np.isclose(np.linalg.norm(quat), 1.):
             raise ValueError("Quaternion must be unit length")
 
-        if ordering is 'xyzw':
+        if ordering == 'xyzw':
             qx, qy, qz, qw = quat
-        elif ordering is 'wxyz':
+        elif ordering == 'wxyz':
             qw, qx, qy, qz = quat
         else:
             raise ValueError(
@@ -295,9 +295,9 @@ def to_quaternion(self, ordering='wxyz'):
             qz = (R[1, 0] - R[0, 1]) / d
 
         # Check ordering last
-        if ordering is 'xyzw':
+        if ordering == 'xyzw':
             quat = np.array([qx, qy, qz, qw])
-        elif ordering is 'wxyz':
+        elif ordering == 'wxyz':
             quat = np.array([qw, qx, qy, qz])
         else:
             raise ValueError(
@@ -384,9 +384,9 @@ class SO3Quaternion(_base.VectorLieGroupBase):
     dof = 3
 
     def from_array(self, arr, ordering='wxyz'):
-        if ordering is 'xyzw':
+        if ordering == 'xyzw':
             self.data = arr[[3, 0, 1, 2]]
-        elif ordering is 'wxyz':
+        elif ordering == 'wxyz':
             self.data = arr
         else:
             raise ValueError(
diff --git a/liegroups/torch/so3.py b/liegroups/torch/so3.py
index 1495c25..1d317c3 100644
--- a/liegroups/torch/so3.py
+++ b/liegroups/torch/so3.py
@@ -68,12 +68,12 @@ def from_quaternion(cls, quat, ordering='wxyz'):
         if not utils.allclose(quat.norm(p=2, dim=1), 1.):
             raise ValueError("Quaternions must be unit length")
 
-        if ordering is 'xyzw':
+        if ordering == 'xyzw':
             qx = quat[:, 0]
             qy = quat[:, 1]
             qz = quat[:, 2]
             qw = quat[:, 3]
-        elif ordering is 'wxyz':
+        elif ordering == 'wxyz':
             qw = quat[:, 0]
             qx = quat[:, 1]
             qy = quat[:, 2]
@@ -359,12 +359,12 @@ def to_quaternion(self, ordering='wxyz'):
             qz[far_zero_inds] = (R_fz[:, 1, 0] - R_fz[:, 0, 1]) / d
 
         # Check ordering last
-        if ordering is 'xyzw':
+        if ordering == 'xyzw':
             quat = torch.cat([qx.unsqueeze_(dim=1),
                               qy.unsqueeze_(dim=1),
                               qz.unsqueeze_(dim=1),
                               qw.unsqueeze_(dim=1)], dim=1).squeeze_()
-        elif ordering is 'wxyz':
+        elif ordering == 'wxyz':
             quat = torch.cat([qw.unsqueeze_(dim=1),
                               qx.unsqueeze_(dim=1),
                               qy.unsqueeze_(dim=1),