diff --git a/binder/postBuild b/binder/postBuild
index 5730bb4..d29dc54 100755
--- a/binder/postBuild
+++ b/binder/postBuild
@@ -30,7 +30,7 @@ def _(*args, **kwargs):
 _(sys.executable, "-m", "pip", "check")
 
 # install jupyterlab pre-release
-_(sys.executable, "-m", "pip", "install", "-U", "--pre", "'jupyterlab>=4.1.0a3,<5'")
+_(sys.executable, "-m", "pip", "install", "-U", "--pre", "jupyterlab>=4.1.0a3,<5")
 
 # install the labextension
 _(sys.executable, "-m", "pip", "install", "-e", ".")
diff --git a/src/index.ts b/src/index.ts
index aa3f494..ee9b692 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -161,7 +161,7 @@ class TransformersInlineProvider implements IInlineCompletionProvider {
       'text/x-latex',
       'text/x-rsrc'
     ];
-    const isText = textMimeTypes.includes(request.mimeType);
+    const isText = textMimeTypes.includes(request.mimeType!);
     // TODO add a setting to only invoke on text if explicitly asked (triggerKind = invoke)
     const model = isText ? this._settings.textModel : this._settings.codeModel;