--- a/google/api_core/operations_v1/transports/rest.py
+++ b/google/api_core/operations_v1/transports/rest.py
@@ -29,9 +29,13 @@
 from google.longrunning import operations_pb2  # type: ignore
 from google.protobuf import empty_pb2  # type: ignore
 from google.protobuf import json_format  # type: ignore
+import google.protobuf
+
 import grpc
 from .base import DEFAULT_CLIENT_INFO as BASE_DEFAULT_CLIENT_INFO, OperationsTransport
 
+PROTOBUF_VERSION = google.protobuf.__version__
+
 OptionalRetry = Union[retries.Retry, object]
 
 DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo(
@@ -184,11 +188,22 @@ def _list_operations(
                 "google.longrunning.Operations.ListOperations"
             ]
 
-        request_kwargs = json_format.MessageToDict(
-            request,
-            preserving_proto_field_name=True,
-            including_default_value_fields=True,
-        )
+        # For backwards compatibility with protobuf 3.x 4.x
+        # Remove once support for protobuf 3.x and 4.x is dropped
+        # https://github.com/googleapis/python-api-core/issues/643
+        if PROTOBUF_VERSION[0:2] in ["3.", "4."]:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                including_default_value_fields=True,  # type: ignore # backward compatibility
+            )
+        else:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                always_print_fields_with_no_presence=True,
+            )
+
         transcoded_request = path_template.transcode(http_options, **request_kwargs)
 
         uri = transcoded_request["uri"]
@@ -199,7 +214,6 @@ def _list_operations(
         json_format.ParseDict(transcoded_request["query_params"], query_params_request)
         query_params = json_format.MessageToDict(
             query_params_request,
-            including_default_value_fields=False,
             preserving_proto_field_name=False,
             use_integers_for_enums=False,
         )
@@ -265,11 +279,22 @@ def _get_operation(
                 "google.longrunning.Operations.GetOperation"
             ]
 
-        request_kwargs = json_format.MessageToDict(
-            request,
-            preserving_proto_field_name=True,
-            including_default_value_fields=True,
-        )
+        # For backwards compatibility with protobuf 3.x 4.x
+        # Remove once support for protobuf 3.x and 4.x is dropped
+        # https://github.com/googleapis/python-api-core/issues/643
+        if PROTOBUF_VERSION[0:2] in ["3.", "4."]:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                including_default_value_fields=True,  # type: ignore # backward compatibility
+            )
+        else:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                always_print_fields_with_no_presence=True,
+            )
+
         transcoded_request = path_template.transcode(http_options, **request_kwargs)
 
         uri = transcoded_request["uri"]
@@ -280,7 +305,6 @@ def _get_operation(
         json_format.ParseDict(transcoded_request["query_params"], query_params_request)
         query_params = json_format.MessageToDict(
             query_params_request,
-            including_default_value_fields=False,
             preserving_proto_field_name=False,
             use_integers_for_enums=False,
         )
@@ -339,11 +363,21 @@ def _delete_operation(
                 "google.longrunning.Operations.DeleteOperation"
             ]
 
-        request_kwargs = json_format.MessageToDict(
-            request,
-            preserving_proto_field_name=True,
-            including_default_value_fields=True,
-        )
+        # For backwards compatibility with protobuf 3.x 4.x
+        # Remove once support for protobuf 3.x and 4.x is dropped
+        # https://github.com/googleapis/python-api-core/issues/643
+        if PROTOBUF_VERSION[0:2] in ["3.", "4."]:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                including_default_value_fields=True,  # type: ignore # backward compatibility
+            )
+        else:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                always_print_fields_with_no_presence=True,
+            )
         transcoded_request = path_template.transcode(http_options, **request_kwargs)
 
         uri = transcoded_request["uri"]
@@ -354,7 +388,6 @@ def _delete_operation(
         json_format.ParseDict(transcoded_request["query_params"], query_params_request)
         query_params = json_format.MessageToDict(
             query_params_request,
-            including_default_value_fields=False,
             preserving_proto_field_name=False,
             use_integers_for_enums=False,
         )
@@ -411,11 +444,21 @@ def _cancel_operation(
                 "google.longrunning.Operations.CancelOperation"
             ]
 
-        request_kwargs = json_format.MessageToDict(
-            request,
-            preserving_proto_field_name=True,
-            including_default_value_fields=True,
-        )
+        # For backwards compatibility with protobuf 3.x 4.x
+        # Remove once support for protobuf 3.x and 4.x is dropped
+        # https://github.com/googleapis/python-api-core/issues/643
+        if PROTOBUF_VERSION[0:2] in ["3.", "4."]:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                including_default_value_fields=True,  # type: ignore # backward compatibility
+            )
+        else:
+            request_kwargs = json_format.MessageToDict(
+                request,
+                preserving_proto_field_name=True,
+                always_print_fields_with_no_presence=True,
+            )
         transcoded_request = path_template.transcode(http_options, **request_kwargs)
 
         # Jsonify the request body
@@ -423,7 +466,6 @@ def _cancel_operation(
         json_format.ParseDict(transcoded_request["body"], body_request)
         body = json_format.MessageToDict(
             body_request,
-            including_default_value_fields=False,
             preserving_proto_field_name=False,
             use_integers_for_enums=False,
         )
@@ -435,7 +477,6 @@ def _cancel_operation(
         json_format.ParseDict(transcoded_request["query_params"], query_params_request)
         query_params = json_format.MessageToDict(
             query_params_request,
-            including_default_value_fields=False,
             preserving_proto_field_name=False,
             use_integers_for_enums=False,
         )
--- a/setup.py
+++ b/setup.py
@@ -30,7 +30,7 @@
 release_status = "Development Status :: 5 - Production/Stable"
 dependencies = [
     "googleapis-common-protos >= 1.56.2, < 2.0.dev0",
-    "protobuf>=3.19.5,<5.0.0.dev0,!=3.20.0,!=3.20.1,!=4.21.0,!=4.21.1,!=4.21.2,!=4.21.3,!=4.21.4,!=4.21.5",
+    "protobuf>=3.19.5,<6.0.0.dev0,!=3.20.0,!=3.20.1,!=4.21.0,!=4.21.1,!=4.21.2,!=4.21.3,!=4.21.4,!=4.21.5",
     "proto-plus >= 1.22.3, <2.0.0dev",
     "google-auth >= 2.14.1, < 3.0.dev0",
     "requests >= 2.18.0, < 3.0.0.dev0",