diff --git a/notebook/app.py b/notebook/app.py
index c3e9b2eec3..084a0f8031 100644
--- a/notebook/app.py
+++ b/notebook/app.py
@@ -56,8 +56,8 @@ def custom_css(self) -> t.Any:
     def get_page_config(self) -> dict[str, t.Any]:
         """Get the page config."""
         config = LabConfig()
-        app = self.extensionapp
-        base_url = self.settings.get("base_url")
+        app: JupyterNotebookApp = self.extensionapp  # type:ignore[assignment]
+        base_url = self.settings.get("base_url", "/")
         page_config_data = self.settings.setdefault("page_config_data", {})
         page_config = {
             **page_config_data,
diff --git a/yarn.lock b/yarn.lock
index 15e689206a..c26db20488 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -17014,21 +17014,21 @@ __metadata:
 
 "typescript@patch:typescript@^3 || ^4#~builtin<compat/typescript>":
   version: 4.9.5
-  resolution: "typescript@patch:typescript@npm%3A4.9.5#~builtin<compat/typescript>::version=4.9.5&hash=289587"
+  resolution: "typescript@patch:typescript@npm%3A4.9.5#~builtin<compat/typescript>::version=4.9.5&hash=23ec76"
   bin:
     tsc: bin/tsc
     tsserver: bin/tsserver
-  checksum: 1f8f3b6aaea19f0f67cba79057674ba580438a7db55057eb89cc06950483c5d632115c14077f6663ea76fd09fce3c190e6414bb98582ec80aa5a4eaf345d5b68
+  checksum: ab417a2f398380c90a6cf5a5f74badd17866adf57f1165617d6a551f059c3ba0a3e4da0d147b3ac5681db9ac76a303c5876394b13b3de75fdd5b1eaa06181c9d
   languageName: node
   linkType: hard
 
 "typescript@patch:typescript@~5.0.2#~builtin<compat/typescript>, typescript@patch:typescript@~5.0.4#~builtin<compat/typescript>":
   version: 5.0.4
-  resolution: "typescript@patch:typescript@npm%3A5.0.4#~builtin<compat/typescript>::version=5.0.4&hash=b5f058"
+  resolution: "typescript@patch:typescript@npm%3A5.0.4#~builtin<compat/typescript>::version=5.0.4&hash=85af82"
   bin:
     tsc: bin/tsc
     tsserver: bin/tsserver
-  checksum: d26b6ba97b6d163c55dbdffd9bbb4c211667ebebc743accfeb2c8c0154aace7afd097b51165a72a5bad2cf65a4612259344ff60f8e642362aa1695c760d303ac
+  checksum: bb309d320c59a26565fb3793dba550576ab861018ff3fd1b7fccabbe46ae4a35546bc45f342c0a0b6f265c801ccdf64ffd68f548f117ceb7f0eac4b805cd52a9
   languageName: node
   linkType: hard