diff --git a/setup.py b/setup.py
index 283fa3d..88de90c 100644
--- a/setup.py
+++ b/setup.py
@@ -27,7 +27,7 @@
 dependencies = [
     "google-api-core[grpc] >= 1.22.2, < 2.0.0dev",
     "proto-plus >= 1.18.1",
-    "grpc-google-iam-v1",
+    "packaging >= 14.3" "grpc-google-iam-v1",
     "six",
 ]
 
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index dd25d17..e5c3a86 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -9,3 +9,4 @@ google-api-core==1.22.2
 proto-plus==1.18.1
 grpc-google-iam-v1==0.12.3
 six==1.13.0
+packaging==14.3