diff --git a/index.js b/index.js
index 49b3650..a690ec8 100644
--- a/index.js
+++ b/index.js
@@ -153,6 +153,15 @@ module.exports = function(api, options = {}) {
           const key = path.toComputedKey()
           if (t.isStringLiteral(key)) {
             const importedId = key.value
+            // Metro uses Jest workers to transform application code. Do not
+            // leak the build worker's ID into the application runtime, where
+            // libraries can mistake it for an actual test environment.
+            if (
+              importedId === 'JEST_WORKER_ID' ||
+              importedId === 'VITEST_WORKER_ID'
+            ) {
+              return
+            }
             const value = (env && importedId in env) ? env[importedId] : process.env[importedId]
             if (value !== undefined) {
               path.replaceWith(t.valueToNode(value))