diff --git a/flask_restx/fields.py b/flask_restx/fields.py
index 18e973a0..00764d01 100644
--- a/flask_restx/fields.py
+++ b/flask_restx/fields.py
@@ -481,6 +481,8 @@ class Float(NumberMixin, Raw):
 
     def format(self, value):
         try:
+            if value is None:
+                return self.default
             return float(value)
         except (ValueError, TypeError) as ve:
             raise MarshallingError(ve)
diff --git a/tests/test_fields.py b/tests/test_fields.py
index e54fb6a9..09b7e271 100644
--- a/tests/test_fields.py
+++ b/tests/test_fields.py
@@ -333,6 +333,12 @@ def test_with_default(self):
         assert not field.required
         assert field.__schema__ == {"type": "number", "default": 0.5}
 
+    def test_none_uses_default(self):
+        field = fields.Float(default=0.5)
+        assert not field.required
+        assert field.__schema__ == {"type": "number", "default": 0.5}
+        assert field.format(None) == 0.5
+
     @pytest.mark.parametrize(
         "value,expected", [("-3.13", -3.13), (str(-3.13), -3.13), (3, 3.0),]
     )