diff --git a/pylinac/ct.py b/pylinac/ct.py
index 13a8f73e0..90a67ffdd 100644
--- a/pylinac/ct.py
+++ b/pylinac/ct.py
@@ -1131,7 +1131,7 @@ def find_phantom_roll(self):
         """
         def is_right_area(region):
             thresh = np.pi * ((self.air_bubble_radius_mm / self.mm_per_pixel) ** 2)
-            return thresh * 1.5 > region.filled_area > thresh / 1.5
+            return thresh * 2 > region.filled_area > thresh / 2
 
         def is_right_eccentricity(region):
             return region.eccentricity < 0.5