diff --git a/setup.py b/setup.py
index 573546bfb..5586eacfa 100644
--- a/setup.py
+++ b/setup.py
@@ -21,7 +21,11 @@
 description = "Client library for the Dialogflow API"
 version = "2.1.2"
 release_status = "Development Status :: 5 - Production/Stable"
-dependencies = ["google-api-core[grpc] >= 1.22.2, < 2.0.0dev", "proto-plus >= 1.10.0"]
+dependencies = [
+    "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
+    "proto-plus >= 1.10.0",
+    "packaging >= 14.3",
+]
 
 package_root = os.path.abspath(os.path.dirname(__file__))
 
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index 25cd0683d..2f5ddda8a 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -7,3 +7,4 @@
 # Then this file should have google-cloud-foo==1.14.0
 google-api-core==1.22.2
 proto-plus==1.10.0
+packaging==14.3