diff --git a/setup.py b/setup.py
index 4df6d538..7d39cbcb 100644
--- a/setup.py
+++ b/setup.py
@@ -32,6 +32,7 @@
     "grpcio >= 1.18.0",
     "grpcio-status >= 1.18.0",
     "overrides>=6.0.1, <7.0.0",
+    "packaging >= 14.3",
 ]
 
 setuptools.setup(
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index aa61acd7..0ed3c3c6 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -7,3 +7,4 @@
 # Then this file should have foo==1.14.0
 google-cloud-pubsub==2.1.0
 overrides==2.0.0
+packaging==14.3