diff --git a/src/Mod/Fem/femsolver/elmer/writer.py b/src/Mod/Fem/femsolver/elmer/writer.py
index 16aec0cfd962..f877588e6a0d 100644
--- a/src/Mod/Fem/femsolver/elmer/writer.py
+++ b/src/Mod/Fem/femsolver/elmer/writer.py
@@ -340,7 +340,8 @@ def _getElectrostaticSolver(self, equation):
     def _handleElectrostaticConstants(self):
         self._constant(
             "Permittivity Of Vacuum",
-            getConstant("PermittivityOfVacuum", "T^4*I^2/(L*M)"))
+            getConstant("PermittivityOfVacuum", "T^4*I^2/(L^3*M)"))
+            # https://forum.freecadweb.org/viewtopic.php?f=18&p=400959#p400959
 
     def _handleElectrostaticMaterial(self, bodies):
         for obj in self._getMember("App::MaterialObject"):
diff --git a/src/Mod/Fem/femtools/constants.py b/src/Mod/Fem/femtools/constants.py
index b0afb7ae4cf8..11a138777aed 100644
--- a/src/Mod/Fem/femtools/constants.py
+++ b/src/Mod/Fem/femtools/constants.py
@@ -41,7 +41,9 @@ def stefan_boltzmann():
 
 
 def permittivity_of_vakuum():
-    return "8.8542e-12 s^4*A^2/(m*kg)"
+    # https://forum.freecadweb.org/viewtopic.php?f=18&p=400959#p400959
+    return "8.8542e-12 s^4*A^2 / (m**3 * kg)"
+
 
 
 def boltzmann_constant():