diff --git a/src/models.rs b/src/models.rs
index 62ea964..83cd3cb 100644
--- a/src/models.rs
+++ b/src/models.rs
@@ -315,13 +315,13 @@ pub struct DocumentResponse {
     /// Current status of OCR processing (pending, processing, completed, failed)
     pub ocr_status: Option<String>,
     /// Original file creation timestamp from source system
-    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     pub original_created_at: Option<DateTime<Utc>>,
     /// Original file modification timestamp from source system
-    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     pub original_modified_at: Option<DateTime<Utc>>,
     /// Additional metadata from source system (permissions, attributes, etc.)
-    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(skip_serializing_if = "Option::is_none", default)]
     pub source_metadata: Option<serde_json::Value>,
 }
 
diff --git a/src/tests/document_response_serialization_tests.rs b/src/tests/document_response_serialization_tests.rs
new file mode 100644
index 0000000..d97741f
--- /dev/null
+++ b/src/tests/document_response_serialization_tests.rs
@@ -0,0 +1,121 @@
+#[cfg(test)]
+mod tests {
+    use crate::models::DocumentResponse;
+    use serde_json;
+    use uuid::Uuid;
+    use chrono::{DateTime, Utc};
+
+    #[test]
+    fn test_document_response_deserializes_without_new_metadata_fields() {
+        // Simulate an old server response without the new metadata fields
+        let old_response_json = r#"{
+            "id": "550e8400-e29b-41d4-a716-446655440000",
+            "filename": "test.pdf",
+            "original_filename": "test.pdf",
+            "file_size": 1024,
+            "mime_type": "application/pdf",
+            "tags": [],
+            "labels": [],
+            "created_at": "2024-01-01T12:00:00Z",
+            "has_ocr_text": false,
+            "ocr_confidence": null,
+            "ocr_word_count": null,
+            "ocr_processing_time_ms": null,
+            "ocr_status": null
+        }"#;
+
+        // Test deserialization - this should work with our serde defaults
+        let result: Result<DocumentResponse, _> = serde_json::from_str(old_response_json);
+        
+        assert!(result.is_ok(), "Should deserialize successfully without metadata fields");
+        
+        let doc = result.unwrap();
+        assert_eq!(doc.filename, "test.pdf");
+        assert!(doc.original_created_at.is_none());
+        assert!(doc.original_modified_at.is_none());
+        assert!(doc.source_metadata.is_none());
+    }
+
+    #[test]
+    fn test_document_response_deserializes_with_new_metadata_fields() {
+        // Simulate a new server response with the metadata fields
+        let new_response_json = r#"{
+            "id": "550e8400-e29b-41d4-a716-446655440000",
+            "filename": "test.pdf",
+            "original_filename": "test.pdf",
+            "file_size": 1024,
+            "mime_type": "application/pdf",
+            "tags": [],
+            "labels": [],
+            "created_at": "2024-01-01T12:00:00Z",
+            "has_ocr_text": false,
+            "ocr_confidence": null,
+            "ocr_word_count": null,
+            "ocr_processing_time_ms": null,
+            "ocr_status": null,
+            "original_created_at": "2023-12-01T10:00:00Z",
+            "original_modified_at": "2023-12-15T15:30:00Z",
+            "source_metadata": {"permissions": "644", "owner": "user1"}
+        }"#;
+
+        // Test deserialization
+        let result: Result<DocumentResponse, _> = serde_json::from_str(new_response_json);
+        
+        assert!(result.is_ok(), "Should deserialize successfully with metadata fields");
+        
+        let doc = result.unwrap();
+        assert_eq!(doc.filename, "test.pdf");
+        assert!(doc.original_created_at.is_some());
+        assert!(doc.original_modified_at.is_some());
+        assert!(doc.source_metadata.is_some());
+        
+        // Verify metadata content
+        let metadata = doc.source_metadata.unwrap();
+        assert_eq!(metadata["permissions"], "644");
+        assert_eq!(metadata["owner"], "user1");
+    }
+
+    #[test]
+    fn test_document_response_serializes_with_metadata_fields() {
+        use crate::models::Document;
+        
+        // Create a test document with metadata
+        let doc = Document {
+            id: Uuid::parse_str("550e8400-e29b-41d4-a716-446655440000").unwrap(),
+            filename: "test.pdf".to_string(),
+            original_filename: "test.pdf".to_string(),
+            file_path: "/test/test.pdf".to_string(),
+            file_size: 1024,
+            mime_type: "application/pdf".to_string(),
+            content: None,
+            ocr_text: None,
+            ocr_confidence: None,
+            ocr_word_count: None,
+            ocr_processing_time_ms: None,
+            ocr_status: None,
+            ocr_error: None,
+            ocr_completed_at: None,
+            tags: vec![],
+            created_at: DateTime::parse_from_rfc3339("2024-01-01T12:00:00Z").unwrap().with_timezone(&Utc),
+            updated_at: DateTime::parse_from_rfc3339("2024-01-01T12:00:00Z").unwrap().with_timezone(&Utc),
+            user_id: Uuid::new_v4(),
+            file_hash: Some("abcd1234".to_string()),
+            original_created_at: Some(DateTime::parse_from_rfc3339("2023-12-01T10:00:00Z").unwrap().with_timezone(&Utc)),
+            original_modified_at: Some(DateTime::parse_from_rfc3339("2023-12-15T15:30:00Z").unwrap().with_timezone(&Utc)),
+            source_metadata: Some(serde_json::json!({"permissions": "644", "owner": "user1"})),
+        };
+
+        // Convert to DocumentResponse
+        let response: DocumentResponse = doc.into();
+        
+        // Serialize to JSON
+        let json = serde_json::to_string(&response).unwrap();
+        
+        // Should contain the metadata fields
+        assert!(json.contains("original_created_at"));
+        assert!(json.contains("original_modified_at"));
+        assert!(json.contains("source_metadata"));
+        assert!(json.contains("permissions"));
+        assert!(json.contains("644"));
+    }
+}
\ No newline at end of file
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
index b137872..6a6eb36 100644
--- a/src/tests/mod.rs
+++ b/src/tests/mod.rs
@@ -19,4 +19,5 @@ mod users_tests;
 mod generic_migration_tests;
 mod migration_constraint_tests;
 mod migration_integration_tests;
-mod failed_documents_unit_tests; 
+mod failed_documents_unit_tests;
+mod document_response_serialization_tests;