diff --git a/src/i18next.d.ts b/src/i18next.d.ts
new file mode 100644
index 0000000..44c1a62
--- /dev/null
+++ b/src/i18next.d.ts
@@ -0,0 +1,7 @@
+import 'i18next';
+
+declare module 'i18next' {
+  interface CustomTypeOptions {
+    returnNull: false;
+  }
+}