diff --git a/setup.py b/setup.py
index 26cc0c6f..aaa121e1 100644
--- a/setup.py
+++ b/setup.py
@@ -27,6 +27,7 @@
     "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
     "grpc-google-iam-v1 >= 0.12.3, < 0.13dev",
     "proto-plus >= 1.4.0",
+    "packaging >= 14.3",
 ]
 
 extras = {"libcst": "libcst >= 0.2.5"}
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index 6fce1954..de982ed0 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -9,3 +9,4 @@ google-api-core==1.22.2
 grpc-google-iam-v1==0.12.3
 proto-plus==1.4.0
 libcst==0.2.5
+packaging==14.3