diff --git a/vizro-core/examples/default/app.py b/vizro-core/examples/default/app.py
index bb0ada9f2..547a718e6 100644
--- a/vizro-core/examples/default/app.py
+++ b/vizro-core/examples/default/app.py
@@ -527,12 +527,14 @@ def create_home_page():
         selector=vm.NavBar(
             items=[
                 vm.NavItem(
+                    text="asdf",
                     pages={
                         "Analysis": ["Homepage", "Variable Analysis"],
                         "Summary": ["Relationship Analysis", "Continent Summary"],
                     },
                 ),
                 vm.NavItem(
+                    text="ASDF",
                     pages=["Country Analysis"],
                     icon="summarize",
                 ),
diff --git a/vizro-core/src/vizro/models/_navigation/accordion.py b/vizro-core/src/vizro/models/_navigation/accordion.py
index fc3b3b58a..2d4606be7 100644
--- a/vizro-core/src/vizro/models/_navigation/accordion.py
+++ b/vizro-core/src/vizro/models/_navigation/accordion.py
@@ -23,7 +23,7 @@ class Accordion(VizroBaseModel):
     """
 
     type: Literal["accordion"] = "accordion"
-    pages: Optional[Dict[str, List[str]]] = Field(
+    pages: Dict[str, List[str]] = Field(
         {}, description="A dictionary with a page group title as key and a list of page IDs as values."
     )
 
diff --git a/vizro-core/src/vizro/models/_navigation/nav_bar.py b/vizro-core/src/vizro/models/_navigation/nav_bar.py
index 5b2a15164..247a2686f 100644
--- a/vizro-core/src/vizro/models/_navigation/nav_bar.py
+++ b/vizro-core/src/vizro/models/_navigation/nav_bar.py
@@ -24,10 +24,10 @@ class NavBar(VizroBaseModel):
     """
 
     type: Literal["navbar"] = "navbar"  # AM: nav_bar?
-    pages: Optional[Dict[str, List[str]]] = Field(
+    pages: Dict[str, List[str]] = Field(
         {}, description="A dictionary with a page group title as key and a list of page IDs as values."
     )
-    items: Optional[List[NavItem]] = []  # AM: think about name
+    items: List[NavItem] = []  # AM: think about name
 
     # validators
     _validate_pages = validator("pages", allow_reuse=True)(_validate_pages)
diff --git a/vizro-core/src/vizro/models/_navigation/nav_item.py b/vizro-core/src/vizro/models/_navigation/nav_item.py
index 92cfc3c59..e5d41d235 100644
--- a/vizro-core/src/vizro/models/_navigation/nav_item.py
+++ b/vizro-core/src/vizro/models/_navigation/nav_item.py
@@ -29,7 +29,7 @@ class NavItem(VizroBaseModel):
     """
 
     type: Literal["navitem"] = "navitem"  # AM: nav_item?
-    pages: Optional[NavPagesType] = []
+    pages: NavPagesType = []
     text: str = Field(
         ..., description="Text to be displayed below the icon."
     )  # AM: Maybe call label. This just does tooltip for now.
diff --git a/vizro-core/src/vizro/models/_navigation/navigation.py b/vizro-core/src/vizro/models/_navigation/navigation.py
index f1ccc3c98..444efaab4 100644
--- a/vizro-core/src/vizro/models/_navigation/navigation.py
+++ b/vizro-core/src/vizro/models/_navigation/navigation.py
@@ -23,8 +23,8 @@ class Navigation(VizroBaseModel):
             Defaults to `None`.
     """
 
-    pages: Optional[NavPagesType] = None  # AM: yes but NavPagesType: note breaking change, maybe put whole type hint in
-    selector: Optional[NavSelectorType] = None
+    pages: NavPagesType = []  # AM: yes but NavPagesType: note breaking change, maybe put whole type hint in
+    selector: NavSelectorType = Accordion()
 
     # validators
     _validate_pages = validator("pages", allow_reuse=True)(_validate_pages)
@@ -33,7 +33,6 @@ class Navigation(VizroBaseModel):
     def pre_build(self):
         # Since models instantiated in pre_build do not themselves have pre_build called on them, we call it manually
         # here. Note that not all selectors have pre_build (Accordion does not).
-        self.selector = self.selector or Accordion()
         self.selector.pages = self.selector.pages or self.pages
         if hasattr(self.selector, "pre_build"):
             self.selector.pre_build()