diff --git a/MaterialLib/MPL/VariableType.cpp b/MaterialLib/MPL/VariableType.cpp
index 7a2e813d572a1934042da3924d572b12dcea6c0c..e14e6fae43f1686ed2d5114080e2b9a20e2c282c 100644
--- a/MaterialLib/MPL/VariableType.cpp
+++ b/MaterialLib/MPL/VariableType.cpp
@@ -48,6 +48,10 @@ Variable convertStringToVariable(std::string const& input)
     {
         return Variable::grain_compressibility;
     }
+    if (boost::iequals(input, "solid_grain_pressure"))
+    {
+        return Variable::solid_grain_pressure;
+    }
 
     OGS_FATAL(
         "The variable name '{:s}' does not correspond to any known variable",
diff --git a/MaterialLib/MPL/VariableType.h b/MaterialLib/MPL/VariableType.h
index 6acd8f21044fac1fc8a24b5191cebc3fb659d67d..85102143c87772f1201b49ed443f39b61484b495 100644
--- a/MaterialLib/MPL/VariableType.h
+++ b/MaterialLib/MPL/VariableType.h
@@ -52,6 +52,7 @@ enum class Variable : int
     liquid_saturation_rate,
     phase_pressure,
     porosity,
+    solid_grain_pressure,
     strain,
     stress,
     temperature,