diff --git a/pybind11_protobuf/BUILD b/pybind11_protobuf/BUILD
index b62eb91..1856ad3 100644
--- a/pybind11_protobuf/BUILD
+++ b/pybind11_protobuf/BUILD
@@ -61,9 +61,11 @@ pybind_library(
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/types:optional",
-        "@com_google_protobuf//:proto_api",
         "@com_google_protobuf//:protobuf",
-    ],
+    ] + select({
+        ":enable_pyproto_api_setting": ["@com_google_protobuf//:proto_api"],
+        "//conditions:default": [],
+    }),
 )
 
 pybind_library(
diff --git a/pybind11_protobuf/proto_cast_util.cc b/pybind11_protobuf/proto_cast_util.cc
index 52c57c9..771e688 100644
--- a/pybind11_protobuf/proto_cast_util.cc
+++ b/pybind11_protobuf/proto_cast_util.cc
@@ -14,9 +14,12 @@
 
 #include "google/protobuf/descriptor.pb.h"
 #include "google/protobuf/descriptor.h"
+#include "google/protobuf/descriptor_database.h"
 #include "google/protobuf/dynamic_message.h"
 #include "google/protobuf/message.h"
+#if defined(PYBIND11_PROTOBUF_ENABLE_PYPROTO_API)
 #include "python/google/protobuf/proto_api.h"
+#endif
 #include "absl/container/flat_hash_map.h"
 #include "absl/strings/numbers.h"
 #include "absl/strings/str_replace.h"
@@ -35,8 +38,12 @@ using ::google::protobuf::FileDescriptor;
 using ::google::protobuf::FileDescriptorProto;
 using ::google::protobuf::Message;
 using ::google::protobuf::MessageFactory;
+#if defined(PYBIND11_PROTOBUF_ENABLE_PYPROTO_API)
 using ::google::protobuf::python::PyProto_API;
 using ::google::protobuf::python::PyProtoAPICapsuleName;
+#else
+struct PyProto_API;
+#endif
 
 namespace pybind11_protobuf {
 namespace {
@@ -321,6 +328,7 @@ py::object GlobalState::PyMessageInstance(const Descriptor* descriptor) {
                        module_name + "?");
 }
 
+#if defined(PYBIND11_PROTOBUF_ENABLE_PYPROTO_API)
 std::pair<py::object, Message*> GlobalState::PyFastCppProtoMessageInstance(
     const Descriptor* descriptor) {
   assert(descriptor != nullptr);
@@ -361,6 +369,7 @@ std::pair<py::object, Message*> GlobalState::PyFastCppProtoMessageInstance(
   }
   return {std::move(result), message};
 }
+#endif
 
 // Create C++ DescriptorPools based on Python DescriptorPools.
 // The Python pool will provide message definitions when they are needed.
@@ -500,6 +509,7 @@ class PythonDescriptorPoolWrapper {
    private:
     bool CopyToFileDescriptorProto(py::handle py_file_descriptor,
                                    FileDescriptorProto* output) {
+#if defined(PYBIND11_PROTOBUF_ENABLE_PYPROTO_API)
       if (GlobalState::instance()->py_proto_api()) {
         try {
           py::object c_proto = py::reinterpret_steal<py::object>(
@@ -518,6 +528,7 @@ class PythonDescriptorPoolWrapper {
           PyErr_Print();
         }
       }
+#endif
 
       py::object wire = py_file_descriptor.attr("serialized_pb");
       const char* bytes = PYBIND11_BYTES_AS_STRING(wire.ptr());
@@ -561,6 +572,9 @@ void ImportProtoDescriptorModule(const Descriptor* descriptor) {
 
 const Message* PyProtoGetCppMessagePointer(py::handle src) {
   assert(PyGILState_Check());
+#ifndef PYBIND11_PROTOBUF_ENABLE_PYPROTO_API
+  return nullptr;
+#else
   if (!GlobalState::instance()->py_proto_api()) return nullptr;
   auto* ptr =
       GlobalState::instance()->py_proto_api()->GetMessagePointer(src.ptr());
@@ -571,6 +585,7 @@ const Message* PyProtoGetCppMessagePointer(py::handle src) {
     return nullptr;
   }
   return ptr;
+#endif
 }
 
 absl::optional<std::string> PyProtoDescriptorName(py::handle py_proto) {
@@ -732,6 +747,9 @@ py::handle GenericPyProtoCast(Message* src, py::return_value_policy policy,
 
 py::handle GenericFastCppProtoCast(Message* src, py::return_value_policy policy,
                                    py::handle parent, bool is_const) {
+#ifndef PYBIND11_PROTOBUF_ENABLE_PYPROTO_API
+  throw std::logic_error("Not implemented");
+#else
   assert(policy != pybind11::return_value_policy::automatic);
   assert(policy != pybind11::return_value_policy::automatic_reference);
   assert(src != nullptr);
@@ -802,6 +820,7 @@ py::handle GenericFastCppProtoCast(Message* src, py::return_value_policy policy,
       std::string message("pybind11_protobuf unhandled return_value_policy::");
       throw py::cast_error(message + ReturnValuePolicyName(policy));
   }
+#endif
 }
 
 py::handle GenericProtoCast(Message* src, py::return_value_policy policy,