diff --git a/packages/metro-babel-transformer/src/index.js b/packages/metro-babel-transformer/src/index.js
index c6782f4a3c..85c4b4cd82 100644
--- a/packages/metro-babel-transformer/src/index.js
+++ b/packages/metro-babel-transformer/src/index.js
@@ -71,7 +71,9 @@ function transform({filename, options, plugins, src}: BabelTransformerArgs) {
 
     return {ast, functionMap};
   } finally {
-    process.env.BABEL_ENV = OLD_BABEL_ENV;
+    if (OLD_BABEL_ENV) {
+      process.env.BABEL_ENV = OLD_BABEL_ENV;
+    }
   }
 }
 
diff --git a/packages/metro-react-native-babel-transformer/src/index.js b/packages/metro-react-native-babel-transformer/src/index.js
index 69904af1c1..f7ae2f5050 100644
--- a/packages/metro-react-native-babel-transformer/src/index.js
+++ b/packages/metro-react-native-babel-transformer/src/index.js
@@ -172,7 +172,9 @@ function transform({filename, options, src, plugins}: BabelTransformerArgs) {
 
     return {ast: result.ast, functionMap};
   } finally {
-    process.env.BABEL_ENV = OLD_BABEL_ENV;
+    if (OLD_BABEL_ENV) {
+      process.env.BABEL_ENV = OLD_BABEL_ENV;
+    }
   }
 }