diff --git a/codegen/core/src/it/resources/META-INF/smithy/main.smithy b/codegen/core/src/it/resources/META-INF/smithy/main.smithy
index 3d7ab539c..27d0c4770 100644
--- a/codegen/core/src/it/resources/META-INF/smithy/main.smithy
+++ b/codegen/core/src/it/resources/META-INF/smithy/main.smithy
@@ -381,6 +381,8 @@ structure Defaults {
     @required
     requiredDefaultBlob: Blob = "c3BhbQ=="
 
+    defaultNullBlob: Blob = null
+
     // timestamp
     @required
     requiredTimestamp: Timestamp
@@ -400,6 +402,8 @@ structure Defaults {
     @required
     requiredDefaultTimestamp: Timestamp = 4.2
 
+    defaultNullTimestamp: Timestamp = null
+
     @required
     requiredList: StringList
 
@@ -420,6 +424,14 @@ structure Defaults {
     @required
     requiredDefaultMap: StringMap = {}
 
+    defaultEnum: StringYesNo = "YES"
+
+    defaultNullEnum: StringYesNo = null
+
+    defaultIntEnum: IntYesNo = 1
+
+    defaultNullIntEnum: IntYesNo = null
+
     @required
     requiredDocument: Document
 
diff --git a/codegen/core/src/main/java/software/amazon/smithy/python/codegen/generators/StructureGenerator.java b/codegen/core/src/main/java/software/amazon/smithy/python/codegen/generators/StructureGenerator.java
index ee29f296e..3b1cffae1 100644
--- a/codegen/core/src/main/java/software/amazon/smithy/python/codegen/generators/StructureGenerator.java
+++ b/codegen/core/src/main/java/software/amazon/smithy/python/codegen/generators/StructureGenerator.java
@@ -288,6 +288,11 @@ private String getDefaultValue(PythonWriter writer, MemberShape member) {
         // see: https://smithy.io/2.0/spec/type-refinement-traits.html#smithy-api-default-trait
         var defaultNode = member.expectTrait(DefaultTrait.class).toNode();
         var target = model.expectShape(member.getTarget());
+        // A null default marks the member nullable and resolves to None. Documents are
+        // excluded since their null default is a non-None Document(None) (see the branch below).
+        if (!target.isDocumentShape() && defaultNode.isNullNode()) {
+            return "None";
+        }
         if (target.isTimestampShape()) {
             ZonedDateTime value = CodegenUtils.parseTimestampNode(model, member, defaultNode);
             return CodegenUtils.getDatetimeConstructor(writer, value);
@@ -318,8 +323,8 @@ private String getDefaultValue(PythonWriter writer, MemberShape member) {
             });
         }
 
+        // A null default is handled by the guard above, so it can't reach here.
         return switch (defaultNode.getType()) {
-            case NULL -> "None";
             case BOOLEAN -> defaultNode.expectBooleanNode().getValue() ? "True" : "False";
             // These will be given to a default_factory in field. They're inherently empty, so no need to
             // worry about any potential values.