diff --git a/src/runtime/mem_bsd.go b/src/runtime/mem_bsd.go
index cc70e806ea..13065b61d4 100644
--- a/src/runtime/mem_bsd.go
+++ b/src/runtime/mem_bsd.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.
 
-// +build dragonfly freebsd nacl netbsd openbsd solaris
+// +build darwin dragonfly freebsd nacl netbsd openbsd solaris
 
 package runtime
 
diff --git a/src/runtime/mem_darwin.go b/src/runtime/mem_darwin.go
deleted file mode 100644
index 75c59f9cdd..0000000000
--- a/src/runtime/mem_darwin.go
+++ /dev/null
@@ -1,62 +0,0 @@
-// Copyright 2010 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package runtime
-
-import "unsafe"
-
-// Don't split the stack as this function may be invoked without a valid G,
-// which prevents us from allocating more stack.
-//go:nosplit
-func sysAlloc(n uintptr, sysStat *uint64) unsafe.Pointer {
-	v, err := mmap(nil, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
-	if err != 0 {
-		return nil
-	}
-	mSysStatInc(sysStat, n)
-	return v
-}
-
-func sysUnused(v unsafe.Pointer, n uintptr) {
-	// Linux's MADV_DONTNEED is like BSD's MADV_FREE.
-	madvise(v, n, _MADV_FREE)
-}
-
-func sysUsed(v unsafe.Pointer, n uintptr) {
-}
-
-// Don't split the stack as this function may be invoked without a valid G,
-// which prevents us from allocating more stack.
-//go:nosplit
-func sysFree(v unsafe.Pointer, n uintptr, sysStat *uint64) {
-	mSysStatDec(sysStat, n)
-	munmap(v, n)
-}
-
-func sysFault(v unsafe.Pointer, n uintptr) {
-	mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE|_MAP_FIXED, -1, 0)
-}
-
-func sysReserve(v unsafe.Pointer, n uintptr) unsafe.Pointer {
-	p, err := mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
-	if err != 0 {
-		return nil
-	}
-	return p
-}
-
-const (
-	_ENOMEM = 12
-)
-
-func sysMap(v unsafe.Pointer, n uintptr, sysStat *uint64) {
-	mSysStatInc(sysStat, n)
-	p, err := mmap(v, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_FIXED|_MAP_PRIVATE, -1, 0)
-	if err == _ENOMEM {
-		throw("runtime: out of memory")
-	}
-	if p != v || err != 0 {
-		throw("runtime: cannot map pages in arena address space")
-	}
-}