diff --git a/packages/next/build/analysis/get-page-static-info.ts b/packages/next/build/analysis/get-page-static-info.ts
index 4c65fa8a2014..6147cf4bebcd 100644
--- a/packages/next/build/analysis/get-page-static-info.ts
+++ b/packages/next/build/analysis/get-page-static-info.ts
@@ -182,7 +182,9 @@ function getMiddlewareConfig(
         matcher(glob)
       } catch (err) {
         throw new Error(
-          `A middleware/edge exported 'config.allowDynamic' is not a valid pattern: ${err.message}`
+          `A middleware/edge exported 'config.allowDynamic' is not a valid pattern: ${
+            (err as Error).message
+          }`
         )
       }
     }