diff --git a/internal/test/components/components.gen.go b/internal/test/components/components.gen.go
index a49865cbf..5a25a7a87 100644
--- a/internal/test/components/components.gen.go
+++ b/internal/test/components/components.gen.go
@@ -880,9 +880,11 @@ func (t OneOfObject10) MarshalJSON() ([]byte, error) {
 		return nil, err
 	}
 	object := make(map[string]json.RawMessage)
-	err = json.Unmarshal(b, &object)
-	if err != nil {
-		return nil, err
+	if t.union != nil {
+		err = json.Unmarshal(b, &object)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	object["one"], err = json.Marshal(t.One)
@@ -1176,9 +1178,11 @@ func (t OneOfObject4) MarshalJSON() ([]byte, error) {
 		return nil, err
 	}
 	object := make(map[string]json.RawMessage)
-	err = json.Unmarshal(b, &object)
-	if err != nil {
-		return nil, err
+	if t.union != nil {
+		err = json.Unmarshal(b, &object)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	object["fixedProperty"], err = json.Marshal(t.FixedProperty)
@@ -1375,9 +1379,11 @@ func (t OneOfObject8) MarshalJSON() ([]byte, error) {
 		return nil, err
 	}
 	object := make(map[string]json.RawMessage)
-	err = json.Unmarshal(b, &object)
-	if err != nil {
-		return nil, err
+	if t.union != nil {
+		err = json.Unmarshal(b, &object)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	object["fixed"], err = json.Marshal(t.Fixed)
@@ -1466,9 +1472,11 @@ func (t OneOfObject9) MarshalJSON() ([]byte, error) {
 		return nil, err
 	}
 	object := make(map[string]json.RawMessage)
-	err = json.Unmarshal(b, &object)
-	if err != nil {
-		return nil, err
+	if t.union != nil {
+		err = json.Unmarshal(b, &object)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	object["type"], err = json.Marshal(t.Type)
diff --git a/internal/test/components/components_test.go b/internal/test/components/components_test.go
index b4f893332..bcb34d752 100644
--- a/internal/test/components/components_test.go
+++ b/internal/test/components/components_test.go
@@ -202,3 +202,13 @@ func TestAnyOf(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, OneOfVariant5{Discriminator: "all", Id: 456}, v5)
 }
+
+func TestMarshalWhenNoUnionValueSet(t *testing.T) {
+	const expected = `{"one":null,"three":null,"two":null}`
+
+	var dst OneOfObject10
+
+	bytes, err := dst.MarshalJSON()
+	assert.Nil(t, err)
+	assert.Equal(t, expected, string(bytes))
+}
diff --git a/pkg/codegen/templates/union.tmpl b/pkg/codegen/templates/union.tmpl
index a29e2d0b7..ac7657dad 100644
--- a/pkg/codegen/templates/union.tmpl
+++ b/pkg/codegen/templates/union.tmpl
@@ -65,9 +65,11 @@
                 return nil, err
             }
             object := make(map[string]json.RawMessage)
-            err = json.Unmarshal(b, &object)
-            if err != nil {
+            if t.union != nil {
+              err = json.Unmarshal(b, &object)
+              if err != nil {
                 return nil, err
+              }
             }
             {{range .Schema.Properties}}
                 object["{{.JsonFieldName}}"], err = json.Marshal(t.{{.GoFieldName}})