diff --git a/s2b_new.go b/s2b_new.go
index aedc448e71..31b623fa45 100644
--- a/s2b_new.go
+++ b/s2b_new.go
@@ -1,4 +1,4 @@
-//go:build go1.20
+//go:build go1.20 || go1.21
 
 package fasthttp
 
diff --git a/s2b_old.go b/s2b_old.go
index 50a034b849..2a0827f712 100644
--- a/s2b_old.go
+++ b/s2b_old.go
@@ -1,4 +1,4 @@
-//go:build !go1.20
+//go:build !go1.20 && !go1.21
 
 package fasthttp