diff --git a/packages/venia-ui/lib/util/formatLocale.js b/packages/venia-ui/lib/util/formatLocale.js
index b10550af3b..3539c67361 100644
--- a/packages/venia-ui/lib/util/formatLocale.js
+++ b/packages/venia-ui/lib/util/formatLocale.js
@@ -15,5 +15,5 @@ export const fromReactIntl = string => {
  * @returns {string} A string (e.g. `fr-FR`).
  */
 export const toReactIntl = string => {
-    return string.replace('_', '-');
+    return string.replace(/_/g, '-');
 };