diff --git a/bolt_riscv64.go b/bolt_riscv64.go
index 2d962d3..07b4b47 100644
--- a/bolt_riscv64.go
+++ b/bolt_riscv64.go
@@ -1,3 +1,5 @@
+// +build riscv64
+
 package bbolt
 
 // maxMapSize represents the largest mmap size supported by Bolt.