diff --git a/packages/wxt/src/client/content-scripts/custom-events.ts b/packages/wxt/src/client/content-scripts/custom-events.ts
index 8b14a1b83..08ca87a26 100644
--- a/packages/wxt/src/client/content-scripts/custom-events.ts
+++ b/packages/wxt/src/client/content-scripts/custom-events.ts
@@ -15,12 +15,5 @@ export class WxtLocationChangeEvent extends Event {
  * Returns an event name unique to the extension and content script that's running.
  */
 export function getUniqueEventName(eventName: string): string {
-  // During the build process, import.meta.env is not defined when importing
-  // entrypoints to get their metadata.
-  const entrypointName =
-    typeof import.meta.env === 'undefined'
-      ? 'build'
-      : import.meta.env.ENTRYPOINT;
-
-  return `${browser?.runtime?.id}:${entrypointName}:${eventName}`;
+  return `${browser?.runtime?.id}:${import.meta.env.ENTRYPOINT}:${eventName}`;
 }
diff --git a/packages/wxt/src/core/utils/building/import-entrypoint.ts b/packages/wxt/src/core/utils/building/import-entrypoint.ts
index 4bfde90cc..d2a029f4d 100644
--- a/packages/wxt/src/core/utils/building/import-entrypoint.ts
+++ b/packages/wxt/src/core/utils/building/import-entrypoint.ts
@@ -112,6 +112,9 @@ function getEsbuildOptions(opts: JitiTransformOptions): TransformOptions {
   return {
     format: 'cjs',
     loader: isJsx ? 'tsx' : 'ts',
+    define: {
+      'import.meta.env.ENTRYPOINT': '"build"',
+    },
     ...(isJsx
       ? {
           // `h` and `Fragment` are undefined, but that's OK because JSX is never evaluated while