diff --git a/setup.py b/setup.py
index 7f03abe..c5d4550 100644
--- a/setup.py
+++ b/setup.py
@@ -42,6 +42,7 @@
     install_requires=(
         "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
         "proto-plus >= 1.4.0",
+        "packaging >= 14.3",
     ),
     python_requires=">=3.6",
     classifiers=[
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index a37a34a..aab6847 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-api-core==1.22.2
 proto-plus==1.4.0
+packaging==14.3