diff --git a/src/cmd/go/internal/mmap/mmap_other.go b/src/cmd/go/internal/mmap/mmap_plan9.go
similarity index 93%
rename from src/cmd/go/internal/mmap/mmap_other.go
rename to src/cmd/go/internal/mmap/mmap_plan9.go
index 269fe8d60a..faa5d5fc66 100644
--- a/src/cmd/go/internal/mmap/mmap_other.go
+++ b/src/cmd/go/internal/mmap/mmap_plan9.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build plan9 || solaris
-
 package mmap
 
 import (
diff --git a/src/cmd/go/internal/mmap/mmap_unix.go b/src/cmd/go/internal/mmap/mmap_unix.go
index 33e839c217..53bcbb92a8 100644
--- a/src/cmd/go/internal/mmap/mmap_unix.go
+++ b/src/cmd/go/internal/mmap/mmap_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build unix && !solaris
+//go:build unix
 
 package mmap