diff --git a/src/pqm/pqm.py b/src/pqm/pqm.py
index 761e533..ee8c62a 100644
--- a/src/pqm/pqm.py
+++ b/src/pqm/pqm.py
@@ -135,7 +135,10 @@ def pqm_chi2(
     chi2_stat, _, dof, _ = _pqm_test(x_samples, y_samples, num_refs, whiten)
     if dof != num_refs - 1:
         # Rescale chi2 to new value which has the same cumulative probability
-        cp = chi2.sf(chi2_stat, dof)
-        chi2_stat = chi2.isf(cp, num_refs - 1)
+        if chi2_stat / dof < 10:
+            cp = chi2.sf(chi2_stat, dof)
+            chi2_stat = chi2.isf(cp, num_refs - 1)
+        else:
+            chi2_stat = chi2_stat * (num_refs - 1) / dof
         dof = num_refs - 1
     return chi2_stat, dof