diff --git a/models.py b/models.py
index 9c4ec41..c1d99bf 100644
--- a/models.py
+++ b/models.py
@@ -26,6 +26,7 @@ class BookIn(BaseModel):
 
     title: str
     author: str
+    publisher: str
 
 
 class BookOut(BaseModel):
diff --git a/repositories.py b/repositories.py
index dc9ff88..4fa11e7 100644
--- a/repositories.py
+++ b/repositories.py
@@ -4,7 +4,7 @@
 
 # Create a new book
 def create_book(db: Session, book: models.BookIn):
-    db_book = models.Book(title=book.title, author=book.author)
+    db_book = models.Book(title=book.title, author=book.author, publisher=book.publisher)
     db.add(db_book)
     db.commit()
     db.refresh(db_book)
@@ -27,6 +27,7 @@ def update_book(db: Session, book_id: int, book: models.BookIn):
     if db_book:
         db_book.title = book.title
         db_book.author = book.author
+        db_book.publisher = book.publisher
         db.commit()
         db.refresh(db_book)
         return db_book
diff --git a/test_main.py b/test_main.py
index 3fea397..2755e9e 100644
--- a/test_main.py
+++ b/test_main.py
@@ -5,8 +5,8 @@
 
 # Test data constants
 TEST_BOOKS = [
-    {"title": "Carrie", "author": "Stephen King"},
-    {"title": "Ready Player One", "author": "Ernest Cline"},
+    {"title": "Carrie", "author": "Stephen King", "publisher": "Scribner"},
+    {"title": "Ready Player One", "author": "Ernest Cline", "publisher": "Crown Publishing Group"},
 ]
 
 class TestMainApp:
@@ -26,6 +26,7 @@ def test_create_book(self, test_db):
         book = create_book(test_db, BookIn(**TEST_BOOKS[0]))
         assert book.title == TEST_BOOKS[0]["title"]
         assert book.author == TEST_BOOKS[0]["author"]
+        assert book.publisher == TEST_BOOKS[0]["publisher"]
         assert book.id is not None
 
     def test_get_books(self, test_db):
@@ -57,7 +58,7 @@ def test_update_book(self, test_db):
 
     def test_delete_book(self, test_db):
         """Test deleting a book"""
-        book = create_book(test_db, BookIn(title="To Delete", author="Author"))
+        book = create_book(test_db, BookIn(title="To Delete", author="Author", publisher="Unknown"))
         deleted_book = delete_book(test_db, book.id)
 
         assert deleted_book is not None
@@ -67,5 +68,5 @@ def test_delete_book(self, test_db):
     def test_nonexistent_operations(self, test_db):
         """Test operations on nonexistent books"""
         assert get_book(test_db, 999999) is None
-        assert update_book(test_db, 999999, BookIn(title="Test", author="Test")) is None
+        assert update_book(test_db, 999999, BookIn(title="Test", author="Test", publisher="Test Publisher")) is None
         assert delete_book(test_db, 999999) is None