diff --git a/include/cantera/thermo/ConstDensityThermo.h b/include/cantera/thermo/ConstDensityThermo.h
index e7fa51ed4..37617e5a2 100644
--- a/include/cantera/thermo/ConstDensityThermo.h
+++ b/include/cantera/thermo/ConstDensityThermo.h
@@ -24,13 +24,19 @@ namespace Cantera
  * The density is assumed to be constant, no matter what the concentration of
  * the solution.
  *
+ * @deprecated To be removed after Cantera 2.5.0. Replaceable with LatticePhase
+ * or IdealSolidSolnPhase
+ *
  * @ingroup thermoprops
  */
 class ConstDensityThermo : public ThermoPhase
 {
 public:
     //! Constructor.
-    ConstDensityThermo() {}
+    ConstDensityThermo() {
+      warn_deprecated("class ConstDensityThermo", "To be removed after Cantera "
+        "2.5.0. Consider replacing with LatticePhase or IdealSolidSolnPhase\n");
+    }
 
     virtual std::string type() const {
         return "ConstDensity";
diff --git a/interfaces/cython/cantera/ctml_writer.py b/interfaces/cython/cantera/ctml_writer.py
index 7ba51e691..de424b038 100644
--- a/interfaces/cython/cantera/ctml_writer.py
+++ b/interfaces/cython/cantera/ctml_writer.py
@@ -2137,7 +2137,16 @@ class semiconductor(phase):
 
 
 class incompressible_solid(phase):
-    """An incompressible solid."""
+    """An incompressible solid.
+
+    .. deprecated:: 2.5
+
+        To be deprecated with version 2.5, and removed thereafter.
+        This phase pointed to an ill-considered constant_density ThermoPhase
+        model, which assumed a constant mass density. This underlying phase is
+        simultaneously being deprecated. Please consider switching to
+        either `IdealSolidSolution` or `lattice` phase, instead.
+    """
     def __init__(self,
                  name = '',
                  elements = '',