diff --git a/src/os/user/lookup_plan9.go b/src/os/user/lookup_plan9.go
index 51caf55935..07939363e7 100644
--- a/src/os/user/lookup_plan9.go
+++ b/src/os/user/lookup_plan9.go
@@ -20,6 +20,7 @@ const (
 func init() {
 	userImplemented = false
 	groupImplemented = false
+	groupListImplemented = false
 }
 
 func current() (*User, error) {
diff --git a/src/os/user/lookup_stubs.go b/src/os/user/lookup_stubs.go
index c975a11964..d8e3d4866a 100644
--- a/src/os/user/lookup_stubs.go
+++ b/src/os/user/lookup_stubs.go
@@ -16,7 +16,7 @@ import (
 )
 
 func init() {
-	groupImplemented = false
+	groupListImplemented = false
 }
 
 func current() (*User, error) {
diff --git a/src/os/user/lookup_unix.go b/src/os/user/lookup_unix.go
index 97c611fad4..dffea4a885 100644
--- a/src/os/user/lookup_unix.go
+++ b/src/os/user/lookup_unix.go
@@ -18,13 +18,15 @@ import (
 	"strings"
 )
 
-const groupFile = "/etc/group"
-const userFile = "/etc/passwd"
+const (
+	groupFile = "/etc/group"
+	userFile  = "/etc/passwd"
+)
 
 var colon = []byte{':'}
 
 func init() {
-	groupImplemented = false
+	groupListImplemented = false
 }
 
 // lineFunc returns a value, an error, or (nil, nil) to skip the row.
diff --git a/src/os/user/user.go b/src/os/user/user.go
index c1b8101c86..4e1b5b3407 100644
--- a/src/os/user/user.go
+++ b/src/os/user/user.go
@@ -20,9 +20,12 @@ import (
 	"strconv"
 )
 
+// These may be set to false in init() for a particular platform and/or
+// build flags to let the tests know to skip tests of some features.
 var (
-	userImplemented  = true // set to false by lookup_stubs.go's init
-	groupImplemented = true // set to false by lookup_stubs.go's init
+	userImplemented      = true
+	groupImplemented     = true
+	groupListImplemented = true
 )
 
 // User represents a user account.
diff --git a/src/os/user/user_test.go b/src/os/user/user_test.go
index 1112c78c00..d8a465edac 100644
--- a/src/os/user/user_test.go
+++ b/src/os/user/user_test.go
@@ -119,8 +119,15 @@ func TestLookupGroup(t *testing.T) {
 	}
 }
 
+func checkGroupList(t *testing.T) {
+	t.Helper()
+	if !groupListImplemented {
+		t.Skip("user: group list not implemented; skipping test")
+	}
+}
+
 func TestGroupIds(t *testing.T) {
-	checkGroup(t)
+	checkGroupList(t)
 	if runtime.GOOS == "aix" {
 		t.Skip("skipping GroupIds, see golang.org/issue/30563")
 	}