diff --git a/tests/test_ptc.py b/tests/test_ptc.py
index 8914235c..ca1627f2 100644
--- a/tests/test_ptc.py
+++ b/tests/test_ptc.py
@@ -419,7 +419,7 @@ def test_covAstier(self):
             means = ptc.finalMeans[ampName][nanMask]
             covModel = ptc.covariancesModel[ampName][nanMask]
             covariancesModel = ptc.evalPtcModel(means, setBtoZero=False)[ampName]
-            self.assertFloatsAlmostEqual(covariancesModel, covModel, atol=1e-13)
+            self.assertFloatsAlmostEqual(covariancesModel, covModel, atol=1e-12)
             # Note that the PhotoTransferCurveDataset does not store the gain
             # fit parameter for FULLCOVARIANCE with b=0, so we can't compare
             # exactly.