diff --git a/setup.py b/setup.py
index 5c46b6c..17a1c5e 100644
--- a/setup.py
+++ b/setup.py
@@ -27,6 +27,7 @@
 dependencies = [
     "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
     "proto-plus >= 1.10.0",
+    "packaging >= 14.3",
 ]
 
 extras = {"libcst": "libcst >= 0.2.5"}
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index 88b0c2f..fd8f2bc 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -8,3 +8,4 @@
 google-api-core==1.22.2
 proto-plus==1.10.0
 libcst==0.2.5
+packaging==14.3