diff --git a/MaterialLib/MPL/Properties/RelativePermeability/RelPermUdell.cpp b/MaterialLib/MPL/Properties/RelativePermeability/RelPermUdell.cpp
index 3bbda2494411a383db124a65334f57323a7d16d1..5e70d82b34a6ac16ed180c37f4b7a67db505cd57 100644
--- a/MaterialLib/MPL/Properties/RelativePermeability/RelPermUdell.cpp
+++ b/MaterialLib/MPL/Properties/RelativePermeability/RelPermUdell.cpp
@@ -97,7 +97,7 @@ PropertyDataType RelPermUdell::dValue(
     auto const dk_rel_LRdse = 3. * s * s;
     auto const dk_rel_LRdsL = dk_rel_LRdse * d_se_d_sL;
 
-    auto const dk_rel_GRdse = 3. * (1. - s) * (1. - s);
+    auto const dk_rel_GRdse = -3. * (1. - s) * (1. - s);
     auto const dk_rel_GRdsL = dk_rel_GRdse * d_se_d_sL;
 
     return Eigen::Vector2d{dk_rel_LRdsL, dk_rel_GRdsL};