diff --git a/masque/utils/transform.py b/masque/utils/transform.py
index dfb6492..90647b1 100644
--- a/masque/utils/transform.py
+++ b/masque/utils/transform.py
@@ -114,9 +114,13 @@ def apply_transforms(
 
     tot = numpy.empty((outer.shape[0], inner.shape[0], 4))
     tot[:, :, :2] = outer[:, None, :2] + xy
-    tot[:, :, 2:] = outer[:, None, 2:] + inner[None, :, 2:]     # sum rotations and mirrored
-    tot[:, :, 2] %= 2 * pi        # clamp rot
-    tot[:, :, 3] %= 2             # clamp mirrored
+
+    # If mirrored, flip inner rotation
+    mirrored_outer = outer[:, None, 3].astype(bool)
+    rotations = outer[:, None, 2] + numpy.where(mirrored_outer, -inner[None, :, 2], inner[None, :, 2])
+
+    tot[:, :, 2] = rotations % (2 * pi)
+    tot[:, :, 3] = (outer[:, None, 3] + inner[None, :, 3]) % 2             # net mirrored
 
     if tensor:
         return tot