diff --git a/proto/_package_info.py b/proto/_package_info.py
index 75e89eba..b2ecfd45 100644
--- a/proto/_package_info.py
+++ b/proto/_package_info.py
@@ -36,14 +36,7 @@ def compile(name, attrs):
     module_name = module.__name__ if hasattr(module, __name__) else ""
     proto_module = getattr(module, "__protobuf__", object())
 
-    # A package should be present; get the marshal from there.
-    # TODO: Revert to empty string as a package value after protobuf fix.
-    # When package is empty, upb based protobuf fails with an
-    # "TypeError: Couldn't build proto file into descriptor pool: invalid name: empty part ()' means"
-    # during an attempt to add to descriptor pool.
-    package = getattr(
-        proto_module, "package", module_name if module_name else "_default_package"
-    )
+    package = getattr(proto_module, "package", module_name if module_name else "")
     marshal = Marshal(name=getattr(proto_module, "marshal", package))
 
     # Done; return the data.
diff --git a/setup.py b/setup.py
index 670bca40..79cd04ee 100644
--- a/setup.py
+++ b/setup.py
@@ -36,7 +36,7 @@
     long_description=README,
     platforms="Posix; MacOS X",
     include_package_data=True,
-    install_requires=("protobuf >= 3.19.0, <5.0.0dev",),
+    install_requires=("protobuf >= 4.21.6, <5.0.0dev",),
     extras_require={
         "testing": [
             "google-api-core[grpc] >= 1.31.5",