diff --git a/clif/python/BUILD b/clif/python/BUILD
index ece0314..aa91ff3 100644
--- a/clif/python/BUILD
+++ b/clif/python/BUILD
@@ -52,7 +52,9 @@ cc_library(
     visibility = ["//visibility:public"],
     deps = [
         ":pickle_support_lib",
+        "//net/proto2/proto:descriptor_cc_proto",
         "//third_party/protobuf/io",
+        "//third_party/pybind11_abseil/compat:py_base_utilities",
         "@com_google_absl//absl/base:config",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/log",
diff --git a/clif/python/pyproto.cc b/clif/python/pyproto.cc
index 872c4ba..8f8d29c 100644
--- a/clif/python/pyproto.cc
+++ b/clif/python/pyproto.cc
@@ -22,13 +22,16 @@ headers are included.
 
 #include <Python.h>
 
+#include <cstdint>
 #include <string>
 
 #include "absl/log/check.h"
+#include "absl/log/log.h"
 #include "clif/python/runtime.h"
 #include "google/protobuf/io/coded_stream.h"
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/dynamic_message.h"
+#include "third_party/pybind11_abseil/compat/py_base_utilities.h"
 
 namespace {
 
@@ -95,6 +98,138 @@ PyObject* GetMessageName(PyObject* py) {
   }
   return fn;
 }
+
+class ClifDescriptorDatabase : public proto2::DescriptorDatabase {
+ public:
+  ClifDescriptorDatabase() {
+    using pybind11_abseil::compat::py_base_utilities::
+        PyExcFetchMaybeErrOccurred;
+    PyObject* descriptor_pool =
+        PyImport_ImportModule("google.protobuf.descriptor_pool");
+    if (descriptor_pool == nullptr) {
+      LOG(FATAL) << "Failed to import google.protobuf.descriptor_pool module: "
+                 << PyExcFetchMaybeErrOccurred().FlatMessage();
+    }
+
+    pool_ = PyObject_CallMethod(descriptor_pool, "Default", nullptr);
+    if (pool_ == nullptr) {
+      LOG(FATAL) << "Failed to get python Default pool: "
+                 << PyExcFetchMaybeErrOccurred().FlatMessage();
+    }
+    Py_DECREF(descriptor_pool);
+  };
+
+  ~ClifDescriptorDatabase() {
+    // Objects of this class are meant to be `static`ally initialized and
+    // never destroyed. This is a commonly used approach, because the order
+    // in which destructors of static objects run is unpredictable. In
+    // particular, it is possible that the Python interpreter may have been
+    // finalized already.
+    DLOG(FATAL) << "MEANT TO BE UNREACHABLE.";
+  };
+
+  bool FindFileByName(const std::string& filename,
+                      proto2::FileDescriptorProto* output) override {
+    PyObject* pyfile_name =
+        PyUnicode_FromStringAndSize(filename.data(), filename.size());
+    if (pyfile_name == nullptr) {
+      // Ideally this would be raise from.
+      PyErr_Format(PyExc_TypeError, "Fail to convert proto file name");
+      return false;
+    }
+
+    PyObject* pyfile =
+        PyObject_CallMethod(pool_, "FindFileByName", "O", pyfile_name);
+    Py_DECREF(pyfile_name);
+    if (pyfile == nullptr) {
+      // Ideally this would be raise from.
+      PyErr_Format(PyExc_TypeError, "Default python pool fail to find %s",
+                   filename.data());
+      return false;
+    }
+
+    PyObject* pyfile_serialized =
+        PyObject_GetAttrString(pyfile, "serialized_pb");
+    Py_DECREF(pyfile);
+    if (pyfile_serialized == nullptr) {
+      // Ideally this would be raise from.
+      PyErr_Format(PyExc_TypeError,
+                   "Python file has no attribute 'serialized_pb'");
+      return false;
+    }
+
+    bool ok = output->ParseFromArray(
+        reinterpret_cast<uint8_t*>(PyBytes_AS_STRING(pyfile_serialized)),
+        PyBytes_GET_SIZE(pyfile_serialized));
+    if (!ok) {
+      LOG(ERROR) << "Failed to parse descriptor for " << filename;
+    }
+    Py_DECREF(pyfile_serialized);
+    return ok;
+  }
+
+  bool FindFileContainingSymbol(const std::string& symbol_name,
+                                proto2::FileDescriptorProto* output) override {
+    return false;
+  }
+
+  bool FindFileContainingExtension(
+      const std::string& containing_type, int field_number,
+      proto2::FileDescriptorProto* output) override {
+    return false;
+  }
+
+  PyObject* pool() { return pool_; }
+
+ private:
+  PyObject* pool_;
+};
+
+const proto2::Descriptor* FindMessageDescriptor(
+    PyObject* pyfile, const char* descritor_full_name) {
+  static auto* database = new ClifDescriptorDatabase();
+  static auto* pool = new proto2::DescriptorPool(database);
+  PyObject* pyfile_name = PyObject_GetAttrString(pyfile, "name");
+  if (pyfile_name == nullptr) {
+    // Ideally this would be raise from.
+    PyErr_Format(PyExc_TypeError, "FileDescriptor has no attribute 'name'");
+    return nullptr;
+  }
+  PyObject* pyfile_pool = PyObject_GetAttrString(pyfile, "pool");
+  if (pyfile_pool == nullptr) {
+    Py_DECREF(pyfile_name);
+    // Ideally this would be raise from.
+    PyErr_Format(PyExc_TypeError, "FileDescriptor has no attribute 'pool'");
+    return nullptr;
+  }
+  bool is_from_generated_pool = database->pool() == pyfile_pool;
+  Py_DECREF(pyfile_pool);
+  const char* pyfile_name_char_ptr = PyUnicode_AsUTF8(pyfile_name);
+  if (pyfile_name_char_ptr == nullptr) {
+    Py_DECREF(pyfile_name);
+    // Ideally this would be raise from.
+    PyErr_Format(PyExc_TypeError,
+                 "FileDescriptor 'name' PyUnicode_AsUTF8() failure.");
+    return nullptr;
+  }
+  if (!is_from_generated_pool) {
+    PyErr_Format(PyExc_TypeError, "%s is not from generated pool",
+                 pyfile_name_char_ptr);
+    Py_DECREF(pyfile_name);
+    return nullptr;
+  }
+  pool->FindFileByName(pyfile_name_char_ptr);
+  Py_DECREF(pyfile_name);
+
+  return pool->FindMessageTypeByName(descritor_full_name);
+}
+
+proto2::DynamicMessageFactory* GetFactory() {
+  static proto2::DynamicMessageFactory* factory =
+      new proto2::DynamicMessageFactory;
+  return factory;
+}
+
 }  // namespace proto
 
 bool Internal_Clif_PyObjAs(PyObject* py, std::unique_ptr<::proto2::Message>* c,
@@ -110,15 +245,42 @@ bool Internal_Clif_PyObjAs(PyObject* py, std::unique_ptr<::proto2::Message>* c,
   }
   const proto2::Descriptor* d = dp->FindMessageTypeByName(
       PyUnicode_AsUTF8(fn));
+  proto2::Message* m;
   if (d == nullptr) {
-    PyErr_Format(PyExc_TypeError, "DESCRIPTOR.full_name %s not found",
-                 PyUnicode_AsUTF8(fn));
-    Py_DECREF(fn);
-    return false;
+    PyObject* pyd = PyObject_GetAttrString(py, "DESCRIPTOR");
+    if (pyd == nullptr) {
+      if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
+        PyErr_Format(PyExc_TypeError, "'%s' %s has no attribute 'DESCRIPTOR'",
+                     ClassName(py), ClassType(py));
+      }
+      return false;
+    }
+
+    PyObject* pyfile = PyObject_GetAttrString(pyd, "file");
+    Py_DECREF(pyd);
+    if (pyfile == nullptr) {
+      PyErr_Format(PyExc_TypeError, "'%s.DESCRIPTOR' has no attribute 'file'",
+                   ClassName(py));
+      return false;
+    }
+
+    const char* descritor_full_name = PyUnicode_AsUTF8(fn);
+    if (descritor_full_name == nullptr) {
+      PyErr_Format(PyExc_ValueError, "Fail to convert descriptor full name");
+    }
+
+    d = proto::FindMessageDescriptor(pyfile, descritor_full_name);
+    Py_DECREF(pyfile);
+    if (d == nullptr) {
+      PyErr_Format(PyExc_ValueError, "Fail to find descriptor %s.",
+                   descritor_full_name);
+      return false;
+    }
+    m = proto::GetFactory()->GetPrototype(d)->New();
+  } else {
+    m = proto2::MessageFactory::generated_factory()->GetPrototype(d)->New();
   }
   Py_DECREF(fn);
-  proto2::Message* m = proto2::MessageFactory::generated_factory()->
-      GetPrototype(d)->New();
   if (m == nullptr) {
     PyErr_SetNone(PyExc_MemoryError);
     return false;