diff --git a/bin/update b/bin/update
index efcaafd6..1c9916ee 100755
--- a/bin/update
+++ b/bin/update
@@ -97,7 +97,7 @@ EOF
   end
 
   def supported_ruby_versions
-    ['2.4', '2.3', '2.2', '2.1', '2.0']
+    ['2.5', '2.4', '2.3', '2.2', '2.1', '2.0']
   end
 
   # check ruby version, only version 2.x works