diff --git a/setup.py b/setup.py
index 7db8ad5f27..d1d01a6bde 100644
--- a/setup.py
+++ b/setup.py
@@ -103,8 +103,9 @@
         # Until this issue is closed
         # https://github.com/googleapis/google-cloud-python/issues/10566
         "google-api-core[grpc] >= 1.31.5, <3.0.0dev,!=2.0.*,!=2.1.*,!=2.2.*,!=2.3.0",
-        "proto-plus >= 1.15.0",
-        "packaging >= 14.3",
+        "proto-plus >= 1.15.0, <2.0.0dev",
+        "protobuf >= 3.19.0, <4.0.0dev",
+        "packaging >= 14.3, <22.0.0dev",
         "google-cloud-storage >= 1.32.0, < 3.0.0dev",
         "google-cloud-bigquery >= 1.15.0, < 3.0.0dev",
         "google-cloud-resource-manager >= 1.3.3, < 3.0.0dev",
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index 0380c54f59..acf8ecba0c 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -8,6 +8,7 @@
 google-api-core==1.31.5
 libcst==0.2.5
 proto-plus==1.15.0
+protobuf==3.19.0
 mock==4.0.2
 google-cloud-storage==1.32.0
 google-auth==1.25.0  # TODO: Remove when google-api-core >= 1.26.0 is required