diff --git a/src/Make.inc b/src/Make.inc
index a6edb165a71..8f549f62456 100644
--- a/src/Make.inc
+++ b/src/Make.inc
@@ -121,6 +121,21 @@ HOST_CFLAGS=-I"$(GOROOT)/include" $(HOST_EXTRA_CFLAGS)
 HOST_LDFLAGS=$(HOST_EXTRA_LDFLAGS)
 PWD=$(shell pwd)
 
+# Decide whether use of cgo is okay.
+ifeq ($(CGO_ENABLED),)
+# Default on...
+CGO_ENABLED:=1
+ifeq ($(GOARCH),arm)  # ... but not on ARM
+CGO_ENABLED:=0
+endif
+ifeq ($(GOOS),plan9)  # ... and not on Plan 9
+CGO_ENABLED:=0
+endif
+ifeq ($(GOOS),openbsd)  # ... and not on OpenBSD
+CGO_ENABLED:=0
+endif
+endif
+
 # Make environment more standard.
 LANG:=
 LC_ALL:=C
@@ -130,11 +145,12 @@ GREP_COLORS:=
 export LANG LC_ALL LC_CTYPE GREP_OPTIONS GREP_COLORS
 
 go-env:
-	@echo export GOARCH=$(GOARCH)
-	@echo export GOOS=$(GOOS)
-	@echo export GOHOSTARCH=$(GOHOSTARCH)
-	@echo export GOHOSTOS=$(GOHOSTOS)
-	@echo export O=$O
+	@echo export GOARCH="$(GOARCH)"
+	@echo export GOOS="$(GOOS)"
+	@echo export GOHOSTARCH="$(GOHOSTARCH)"
+	@echo export GOHOSTOS="$(GOHOSTOS)"
+	@echo export CGO_ENABLED="$(CGO_ENABLED)"
+	@echo export O="$O"
 	@echo export AS="$(AS)"
 	@echo export CC="$(CC)"
 	@echo export GC="$(GC)"
diff --git a/src/pkg/net/Makefile b/src/pkg/net/Makefile
index 6b3d0b328ba..cc895f75680 100644
--- a/src/pkg/net/Makefile
+++ b/src/pkg/net/Makefile
@@ -36,9 +36,13 @@ GOFILES_freebsd=\
 	sendfile_stub.go\
 	sock_bsd.go\
 
+ifeq ($(CGO_ENABLED),1)
 CGOFILES_freebsd=\
 	cgo_bsd.go\
-	cgo_unix.go\
+	cgo_unix.go
+else
+GOFILES_freebsd+=cgo_stub.go
+endif
 
 GOFILES_darwin=\
 	dnsclient_unix.go\
@@ -53,9 +57,13 @@ GOFILES_darwin=\
 	sendfile_stub.go\
 	sock_bsd.go\
 
+ifeq ($(CGO_ENABLED),1)
 CGOFILES_darwin=\
 	cgo_bsd.go\
-	cgo_unix.go\
+	cgo_unix.go
+else
+GOFILES_darwin+=cgo_stub.go
+endif
 
 GOFILES_linux=\
 	dnsclient_unix.go\
@@ -69,6 +77,14 @@ GOFILES_linux=\
 	sendfile_linux.go\
 	sock_linux.go\
 
+ifeq ($(CGO_ENABLED),1)
+CGOFILES_linux=\
+	cgo_linux.go\
+	cgo_unix.go
+else
+GOFILES_linux+=cgo_stub.go
+endif
+
 GOFILES_openbsd=\
 	dnsclient.go\
 	dnsconfig.go\
@@ -86,15 +102,6 @@ GOFILES_plan9=\
 	lookup_unix.go\
 	sendfile_stub.go\
 
-ifeq ($(GOARCH),arm)
-# ARM has no cgo, so use the stubs.
-GOFILES_linux+=cgo_stub.go
-else
-CGOFILES_linux=\
-	cgo_linux.go\
-	cgo_unix.go
-endif
-
 GOFILES_windows=\
 	file_windows.go\
 	interface_windows.go\
diff --git a/src/pkg/os/user/Makefile b/src/pkg/os/user/Makefile
index 731f7999ace..aabb54995d2 100644
--- a/src/pkg/os/user/Makefile
+++ b/src/pkg/os/user/Makefile
@@ -8,7 +8,7 @@ TARG=os/user
 GOFILES=\
 	user.go\
 
-ifneq ($(GOARCH),arm)
+ifeq ($(CGO_ENABLED),1)
 CGOFILES_linux=\
 	lookup_unix.go
 CGOFILES_freebsd=\
diff --git a/src/pkg/os/user/lookup_unix.go b/src/pkg/os/user/lookup_unix.go
index 678de802b51..1b2c9e8c993 100644
--- a/src/pkg/os/user/lookup_unix.go
+++ b/src/pkg/os/user/lookup_unix.go
@@ -25,6 +25,10 @@ static int mygetpwuid_r(int uid, struct passwd *pwd,
 */
 import "C"
 
+func init() {
+	implemented = true
+}
+
 // Lookup looks up a user by username. If the user cannot be found,
 // the returned error is of type UnknownUserError.
 func Lookup(username string) (*User, os.Error) {
diff --git a/src/pkg/os/user/user.go b/src/pkg/os/user/user.go
index dd009211d76..f71e11d8b21 100644
--- a/src/pkg/os/user/user.go
+++ b/src/pkg/os/user/user.go
@@ -9,6 +9,8 @@ import (
 	"strconv"
 )
 
+var implemented = false // set to true by lookup_unix.go's init
+
 // User represents a user account.
 type User struct {
 	Uid      int // user id
diff --git a/src/pkg/os/user/user_test.go b/src/pkg/os/user/user_test.go
index ee917b57af2..59f15e4c675 100644
--- a/src/pkg/os/user/user_test.go
+++ b/src/pkg/os/user/user_test.go
@@ -13,8 +13,8 @@ import (
 )
 
 func skip(t *testing.T) bool {
-	if runtime.GOARCH == "arm" {
-		t.Logf("user: cgo not implemented on arm; skipping tests")
+	if !implemented {
+		t.Logf("user: not implemented; skipping tests")
 		return true
 	}
 
diff --git a/src/pkg/runtime/cgo/Makefile b/src/pkg/runtime/cgo/Makefile
index e7a2fa7c64a..766794797f6 100644
--- a/src/pkg/runtime/cgo/Makefile
+++ b/src/pkg/runtime/cgo/Makefile
@@ -4,29 +4,12 @@
 
 include ../../../Make.inc
 
-ENABLED:=1
-
-ifeq ($(GOARCH),arm)
-ENABLED:=0
-endif
-
-ifeq ($(GOOS),plan9)
-ENABLED:=0
-endif
-ifeq ($(GOOS),openbsd)
-ENABLED:=0
-endif
-
-ifeq ($(DISABLE_CGO),1)
-ENABLED:=0
-endif
-
 TARG=runtime/cgo
 
 GOFILES=\
 	cgo.go\
 
-ifeq ($(ENABLED),1)
+ifeq ($(CGO_ENABLED),1)
 
 # Unwarranted chumminess with Make.pkg's cgo rules.
 # Do not try this at home.
@@ -59,7 +42,7 @@ endif
 
 include ../../../Make.pkg
 
-ifeq ($(ENABLED),1)
+ifeq ($(CGO_ENABLED),1)
 _cgo_defun.c:
 	echo >$@
 
diff --git a/src/run.bash b/src/run.bash
index ae79a0cec3f..a9689bf15e9 100755
--- a/src/run.bash
+++ b/src/run.bash
@@ -49,20 +49,20 @@ GOMAXPROCS=10 gomake testshort
 time gomake test
 ) || exit $?
 
-[ "$GOARCH" == arm ] ||
+[ "$CGO_ENABLED" != 1 ] ||
 [ "$GOHOSTOS" == windows ] ||
 (xcd ../misc/cgo/stdio
 gomake clean
 ./test.bash
 ) || exit $?
 
-[ "$GOARCH" == arm ] ||
+[ "$CGO_ENABLED" != 1 ] ||
 (xcd ../misc/cgo/life
 gomake clean
 ./test.bash
 ) || exit $?
 
-[ "$GOARCH" == arm ] ||
+[ "$CGO_ENABLED" != 1 ] ||
 [ "$GOHOSTOS" == windows ] ||
 (xcd ../misc/cgo/test
 gomake clean