diff --git a/src/somd2/runner/_runner.py b/src/somd2/runner/_runner.py
index ad09f2e..93f11f5 100644
--- a/src/somd2/runner/_runner.py
+++ b/src/somd2/runner/_runner.py
@@ -522,8 +522,10 @@ def _repartition_h_mass(system, factor=1.0):
         if not isinstance(factor, float):
             raise TypeError("'factor' must be of type 'float'")
 
+        from math import isclose
+
         # Early exit if no repartitioning is required.
-        if factor == 1.0:
+        if isclose(factor, 1.0, abs_tol=1e-4):
             return
 
         from sire.morph import (