diff --git a/poetry.lock b/poetry.lock
index 84d1b43..7689de4 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1868,4 +1868,4 @@ compiler = ["black", "isort", "jinja2"]
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.7"
-content-hash = "f9503e42026d0807dc3ed344b5f8e6fa3f1c7ffa9c66b086de929aefaa8cb8c6"
+content-hash = "58b357685be67e8852b589ee0df3011b37dc1a2460ece732c0fa4c922f62bddd"
diff --git a/pyproject.toml b/pyproject.toml
index 043f021..6d43e2d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -15,6 +15,7 @@ packages = [
 python = "^3.7"
 black = { version = ">=19.3b0", optional = true }
 grpclib = "^0.4.1"
+importlib-metadata = { version = ">=1.6.0", python = "<3.8" }
 jinja2 = { version = ">=3.0.3", optional = true }
 python-dateutil = "^2.8"
 isort = {version = "^5.11.5", optional = true}
diff --git a/src/betterproto/__init__.py b/src/betterproto/__init__.py
index ed42cf5..6215254 100644
--- a/src/betterproto/__init__.py
+++ b/src/betterproto/__init__.py
@@ -1373,6 +1373,9 @@ class Message(ABC):
                     value = [i.to_pydict(casing, include_default_values) for i in value]
                     if value or include_default_values:
                         output[cased_name] = value
+                elif value is None:
+                    if include_default_values:
+                        output[cased_name] = None
                 elif (
                     value._serialized_on_wire
                     or include_default_values
diff --git a/src/betterproto/_version.py b/src/betterproto/_version.py
index e40ec96..484794b 100644
--- a/src/betterproto/_version.py
+++ b/src/betterproto/_version.py
@@ -1,4 +1,7 @@
-from pkg_resources import get_distribution
+try:
+    from importlib import metadata
+except ImportError:  # for Python<3.8
+    import importlib_metadata as metadata  # type: ignore
 
 
-__version__ = get_distribution("betterproto").version
+__version__ = metadata.version("betterproto")
diff --git a/tests/test_features.py b/tests/test_features.py
index 2deef2b..940cd51 100644
--- a/tests/test_features.py
+++ b/tests/test_features.py
@@ -265,6 +265,32 @@ def test_optional_flag():
     assert Request().parse(b"\n\x00").flag is False
 
 
+def test_optional_datetime_to_dict():
+    @dataclass
+    class Request(betterproto.Message):
+        date: Optional[datetime] = betterproto.message_field(1, optional=True)
+
+    # Check dict serialization
+    assert Request().to_dict() == {}
+    assert Request().to_dict(include_default_values=True) == {"date": None}
+    assert Request(date=datetime(2020, 1, 1)).to_dict() == {
+        "date": "2020-01-01T00:00:00Z"
+    }
+    assert Request(date=datetime(2020, 1, 1)).to_dict(include_default_values=True) == {
+        "date": "2020-01-01T00:00:00Z"
+    }
+
+    # Check pydict serialization
+    assert Request().to_pydict() == {}
+    assert Request().to_pydict(include_default_values=True) == {"date": None}
+    assert Request(date=datetime(2020, 1, 1)).to_pydict() == {
+        "date": datetime(2020, 1, 1)
+    }
+    assert Request(date=datetime(2020, 1, 1)).to_pydict(
+        include_default_values=True
+    ) == {"date": datetime(2020, 1, 1)}
+
+
 def test_to_json_default_values():
     @dataclass
     class TestMessage(betterproto.Message):