diff --git a/setup.py b/setup.py
index 9f24ef7..6036e9a 100644
--- a/setup.py
+++ b/setup.py
@@ -31,6 +31,7 @@
 dependencies = [
     "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
     "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 d071c72..ce07c30 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -7,4 +7,5 @@
 # Then this file should have foo==1.14.0
 google-api-core==1.22.2
 proto-plus==1.4.0
-libcst==0.2.5
\ No newline at end of file
+libcst==0.2.5
+packaging==14.3