diff --git a/src/dendropy/calculate/treemeasure.py b/src/dendropy/calculate/treemeasure.py
index db02b870..e42b57e7 100644
--- a/src/dendropy/calculate/treemeasure.py
+++ b/src/dendropy/calculate/treemeasure.py
@@ -23,13 +23,18 @@
 
 import math
 from dendropy.calculate import phylogeneticdistance
+from dendropy.utility import deprecate
 
 EULERS_CONSTANT = 0.5772156649015328606065120900824024310421
 
-## legacy: will soon be deprecated
+
 class PatristicDistanceMatrix(phylogeneticdistance.PhylogeneticDistanceMatrix):
 
     def __init__(self, tree):
+        deprecate.dendropy_deprecation_warning(
+            message="PatristicDistanceMatrix is deprecated since Dendropy 5. "
+            "Use entropy. phylogenetic distance.PhylogeneticDistanceMatrix instead.",
+        )
         phylogeneticdistance.PhylogeneticDistanceMatrix.__init__(self)
         self.compile_from_tree(tree=tree)