diff --git a/setup.py b/setup.py
index cb84f4ae..ada121f8 100644
--- a/setup.py
+++ b/setup.py
@@ -24,6 +24,7 @@
 dependencies = [
     "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
     "proto-plus >= 1.15.0",
+    "packaging >= 14.3",
 ]
 
 extras = {"libcst": "libcst >= 0.2.5"}
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index cc205f2a..29486a27 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==1.15.0
+packaging==14.3