diff --git a/drizzle/tests/test_utils.py b/drizzle/tests/test_utils.py
index 7badbae..ea91023 100644
--- a/drizzle/tests/test_utils.py
+++ b/drizzle/tests/test_utils.py
@@ -146,7 +146,7 @@ def test_estimate_pixel_scale_ratio():
         assert abs(phi3 - -72.08836985651423) < 1e-14
         assert abs(phi4 - -72.08837650625458) < 1e-14
         pscale1 = _estimate_pixel_scale(w, refpix)
-        assert abs(pscale1 - 1.285368350331663e-07) < 1.e-13
+        assert abs(pscale1 - 1.285368350331663e-07) < 1.e-21
 
         refpix = np.array([512., 512.])
         l1, phi1 = w.pixel_to_world_values(*(refpix - 0.5))
@@ -162,7 +162,7 @@ def test_estimate_pixel_scale_ratio():
         assert abs(phi3 - -72.08349683404813) < 1e-13
         assert abs(phi4 - -72.08350348350724) < 1e-13
         pscale2 = _estimate_pixel_scale(w, refpix)
-        assert abs(pscale2 - 1.285368361004753e-07) < 1.e-13
+        assert abs(pscale2 - 1.285368361004753e-07) < 1.e-21
 
     pscale = estimate_pixel_scale_ratio(w, w, w.wcs.crpix, (0, 0))