diff --git a/setup.py b/setup.py
index 62fb3bbb3..86eb2d41d 100644
--- a/setup.py
+++ b/setup.py
@@ -42,8 +42,8 @@
     "google-cloud-core >= 1.4.1, <3.0.0dev",
     "google-resumable-media >= 0.6.0, < 3.0dev",
     "packaging >= 14.3",
-    "proto-plus >= 1.10.0",  # For the legacy proto-based types.
     "protobuf >= 3.12.0",  # For the legacy proto-based types.
+    "python-dateutil >= 2.7.2, <3.0dev",
     "pyarrow >= 3.0.0, < 8.0dev",
     "requests >= 2.18.0, < 3.0.0dev",
 ]