diff --git a/src/common/index.ts b/src/common/index.ts
index 48c0809..95fb007 100644
--- a/src/common/index.ts
+++ b/src/common/index.ts
@@ -104,7 +104,7 @@ export function loadConfiguration(
       {},
       ...grammars.filter((x) => x.language).map((x) => ({ [x.language || '']: x.scopeName }))
     )
-    let extToLang = Object.assign({}, ...ys.map((x: any) => x.extensions.map((e: any) => ({ [e]: x.id }))).flat())
+    let extToLang = Object.assign({}, ...ys.map((x: any) => (x.extensions || []).map((e: any) => ({ [e]: x.id }))).flat())
     extensionToScope = (ext) => scope || langToScope[extToLang[ext]]
   }
   return { grammars, extensionToScope }