diff --git a/README.md b/README.md
index a9000a0..9854a65 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,8 @@ Inspired by [fluent-plugin-anonymizer](https://github.com/y-ken/fluent-plugin-an
 
 # Requirements
 
-- fluentd: v0.14.x
-- Ruby: 2.4
+- fluentd: v0.14.x or later
+- Ruby: 2.4 or later
 
 # Installation