diff --git a/src/compiler/bundle/core-resolve-plugin.ts b/src/compiler/bundle/core-resolve-plugin.ts
index ebfdeb92f63..e3550ba4f16 100644
--- a/src/compiler/bundle/core-resolve-plugin.ts
+++ b/src/compiler/bundle/core-resolve-plugin.ts
@@ -88,7 +88,7 @@ export const coreResolvePlugin = (config: d.Config, compilerCtx: d.CompilerCtx,
           if (platform === 'worker') {
             return `
 export const Build = {
-  isDev: false,
+  isDev: ${config.devMode},
   isBrowser: true,
   isServer: false,
   isTesting: false,