diff --git a/src/secret-box.ts b/src/secret-box.ts
index 4922c61..ea56b5e 100644
--- a/src/secret-box.ts
+++ b/src/secret-box.ts
@@ -66,7 +66,7 @@ export default class SecretBox {
     log.trace('fromString')
 
     const parts = data.split('.')
-    if (parts.length < 2) {
+    if (parts.length !== 2) {
       log.warn('Invalid parts count')
       return null
     }