diff --git a/setup.py b/setup.py
index 8de1c6c2..2ccf8198 100644
--- a/setup.py
+++ b/setup.py
@@ -26,6 +26,7 @@
 dependencies = [
     "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
     "proto-plus >= 1.4.0",
+    "packaging >= 14.3",
     "libcst >= 0.2.5",
 ]
 extras = {
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index f9a2ecfa..52ae0efd 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -11,3 +11,5 @@ libcst==0.2.5
 fastavro==0.21.2
 pandas==0.21.1
 pyarrow==0.15.0
+packaging==14.3
+google-auth==1.24.0  # TODO: remove when google-auth>=1.25.0 si transitively required through google-api-core