diff --git a/coolest/api/util.py b/coolest/api/util.py
index a54347f..2e41723 100644
--- a/coolest/api/util.py
+++ b/coolest/api/util.py
@@ -215,7 +215,7 @@ def ellipticity_from_moments(light_map, pixel_size):
     q = np.sqrt(lambda_2 / lambda_1)  # b/a, axis ratio
     phi = np.arctan(2. * mu_11_ / (mu_20_ - mu_02_)) / 2.  # position angle
     if mu_02_ > mu_20_:
-        phi += np.pi  # makes it consistent angles conventions in COOLEST
+        phi += np.pi / 2.  # makes it consistent angles conventions in COOLEST
     return phi, q