diff --git a/IBPSA/Fluid/Interfaces/ConservationEquation.mo b/IBPSA/Fluid/Interfaces/ConservationEquation.mo
index 146a02f505..dd6166dc25 100644
--- a/IBPSA/Fluid/Interfaces/ConservationEquation.mo
+++ b/IBPSA/Fluid/Interfaces/ConservationEquation.mo
@@ -170,11 +170,13 @@ protected
 
 initial equation
   // Assert that the substance with name 'water' has been found.
-  assert(Medium.nXi == 0 or abs(sum(s)-1) < 1e-5,
-      "In " + getInstanceName() + ":
+  if use_mWat_flow then
+    assert(Medium.nXi == 0 or abs(sum(s) - 1) < 1e-5, "In " + getInstanceName()
+       + ":
          If Medium.nXi > 1, then substance 'water' must be present for one component of '"
-         + Medium.mediumName + "'.
+       + Medium.mediumName + "'.
          Check medium model.");
+  end if;
 
   // Make sure that if energyDynamics is SteadyState, then
   // massDynamics is also SteadyState.
diff --git a/IBPSA/Fluid/Interfaces/StaticTwoPortConservationEquation.mo b/IBPSA/Fluid/Interfaces/StaticTwoPortConservationEquation.mo
index b3c31c2f9b..c334a23dde 100644
--- a/IBPSA/Fluid/Interfaces/StaticTwoPortConservationEquation.mo
+++ b/IBPSA/Fluid/Interfaces/StaticTwoPortConservationEquation.mo
@@ -108,11 +108,12 @@ protected
     "Needed to connect to conditional connector";
 initial equation
   // Assert that the substance with name 'water' has been found.
-  assert(Medium.nXi == 0 or abs(sum(s)-1) < 1e-5,
+  if use_mWat_flow then
+    assert(Medium.nXi == 0 or abs(sum(s)-1) < 1e-5,
       "If Medium.nXi > 1, then substance 'water' must be present for one component.'"
          + Medium.mediumName + "'.\n"
          + "Check medium model.");
-
+  end if;
 equation
   // Conditional connectors
   connect(mWat_flow, mWat_flow_internal);
diff --git a/IBPSA/Fluid/MixingVolumes/Validation/MSLCombustionAir.mo b/IBPSA/Fluid/MixingVolumes/Validation/MSLCombustionAir.mo
index 26f438f897..8d63ac9eae 100644
--- a/IBPSA/Fluid/MixingVolumes/Validation/MSLCombustionAir.mo
+++ b/IBPSA/Fluid/MixingVolumes/Validation/MSLCombustionAir.mo
@@ -1,8 +1,8 @@
 within IBPSA.Fluid.MixingVolumes.Validation;
 model MSLCombustionAir
   "Test of MSL mixture gas with Modelica IBPSA components"
-   package Medium = Modelica.Media.IdealGases.MixtureGases.CombustionAir; // Doesn't work, substance 'water' is missing
-//   package Medium = Modelica.Media.IdealGases.MixtureGases.FlueGasSixComponents; // Doesn't work
+   //package Medium = Modelica.Media.IdealGases.MixtureGases.CombustionAir; // Doesn't work, substance 'water' is missing
+   package Medium = Modelica.Media.IdealGases.MixtureGases.FlueGasSixComponents; // Doesn't work
   //package Medium = Modelica.Media.IdealGases.SingleGases.N2; // Works fine
 
   parameter Modelica.Units.SI.PressureDifference dp_nominal=1e4;
@@ -22,7 +22,7 @@ model MSLCombustionAir
     redeclare package Medium = Medium,
     nPorts=1)
     annotation (Placement(transformation(extent={{60,-10},{40,10}})));
-  IBPSA.Fluid.MixingVolumes.BaseClasses.MixingVolumeHeatPort vol(
+  IBPSA.Fluid.MixingVolumes.MixingVolume vol(
     redeclare package Medium = Medium,
     m_flow_nominal=m_flow_nominal,
     V=1,
diff --git a/IBPSA/Fluid/MixingVolumes/Validation/package.order b/IBPSA/Fluid/MixingVolumes/Validation/package.order
index 607704e330..a310bfa2b3 100644
--- a/IBPSA/Fluid/MixingVolumes/Validation/package.order
+++ b/IBPSA/Fluid/MixingVolumes/Validation/package.order
@@ -4,6 +4,7 @@ CoupledVolumesSpecializedAirPerfectGas
 CoupledVolumesSpecializedWaterConstantProperties_pT
 CoupledVolumesSpecializedWaterTemperatureDependentDensity
 CoupledVolumesWater
+FixmeMSLCombustionAir
 MSLCombustionAir
 MixingVolume
 MixingVolumeAdiabaticCooling