diff --git a/webhooks_go112.go b/webhooks_go112.go
index 4e0db0e41..b27c342c8 100644
--- a/webhooks_go112.go
+++ b/webhooks_go112.go
@@ -1,3 +1,4 @@
+//go:build !go1.13
 // +build !go1.13
 
 package slack
diff --git a/webhooks_go113.go b/webhooks_go113.go
index 99c243f59..869105d09 100644
--- a/webhooks_go113.go
+++ b/webhooks_go113.go
@@ -1,3 +1,4 @@
+//go:build go1.13
 // +build go1.13
 
 package slack