diff --git a/child.go b/child.go
index 1b5e04d..cd71d1f 100644
--- a/child.go
+++ b/child.go
@@ -82,8 +82,8 @@ func (c *child) String() string {
 	return c.proc.String()
 }
 
-func (c *child) Kill() {
-	c.proc.Signal(os.Kill)
+func (c *child) Kill() error {
+	return c.proc.Signal(os.Kill)
 }
 
 func (c *child) waitExit(result chan<- error, exited chan<- struct{}) {
diff --git a/child_test.go b/child_test.go
index bd32804..2e2f9d2 100644
--- a/child_test.go
+++ b/child_test.go
@@ -30,7 +30,12 @@ func TestChildKill(t *testing.T) {
 
 	proc := <-procs
 
-	go child.Kill()
+	go func() {
+		if err := child.Kill(); err != nil {
+			t.Errorf("Failed to kill child: %s", err)
+		}
+	}()
+
 	if sig := proc.recvSignal(nil); sig != os.Kill {
 		t.Errorf("Received %v instead of os.Kill", sig)
 	}
diff --git a/doc.go b/doc.go
index cc68c13..0e5f6c2 100644
--- a/doc.go
+++ b/doc.go
@@ -13,18 +13,18 @@
 // To use this library with systemd you need to use the PIDFile option in the service
 // file.
 //
-//    [Unit]
-//    Description=Service using tableflip
+//	[Unit]
+//	Description=Service using tableflip
 //
-//    [Service]
-//    ExecStart=/path/to/binary -some-flag /path/to/pid-file
-//    ExecReload=/bin/kill -HUP $MAINPID
-//    PIDFile=/path/to/pid-file
+//	[Service]
+//	ExecStart=/path/to/binary -some-flag /path/to/pid-file
+//	ExecReload=/bin/kill -HUP $MAINPID
+//	PIDFile=/path/to/pid-file
 //
 // Then pass /path/to/pid-file to New. You can use systemd-run to
 // test your implementation:
 //
-//    systemd-run --user -p PIDFile=/path/to/pid-file /path/to/binary
+//	systemd-run --user -p PIDFile=/path/to/pid-file /path/to/binary
 //
 // systemd-run will print a unit name, which you can use with systemctl to
 // inspect the service.
@@ -44,5 +44,4 @@
 // which may be necessary in certain development circumstances, but it will not
 // provide zero downtime upgrades when running on Windows. See the `testing`
 // package for an example of how to use it.
-//
 package tableflip
diff --git a/go.mod b/go.mod
index 7c90929..3aa627f 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@ module github.com/cloudflare/tableflip
 
 go 1.14
 
-require golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4
+require golang.org/x/sys v0.1.0
diff --git a/go.sum b/go.sum
index 9b4cc1b..b69ea85 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,2 @@
-golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
-golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.1.0 h1:kunALQeHf1/185U1i0GOB/fy1IPRDDpuoOOqRReG57U=
+golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
diff --git a/http_example_test.go b/http_example_test.go
index 1180045..6a3b8c8 100644
--- a/http_example_test.go
+++ b/http_example_test.go
@@ -77,5 +77,5 @@ func Example_httpShutdown() {
 	})
 
 	// Wait for connections to drain.
-	server.Shutdown(context.Background())
+	_ = server.Shutdown(context.Background())
 }
diff --git a/tcp_example_test.go b/tcp_example_test.go
index 969bbe2..c4ec273 100644
--- a/tcp_example_test.go
+++ b/tcp_example_test.go
@@ -60,8 +60,8 @@ func Example_tcpServer() {
 			}
 
 			go func() {
-				c.SetDeadline(time.Now().Add(time.Second))
-				c.Write([]byte("It is a mistake to think you can solve any major problems just with potatoes.\n"))
+				_ = c.SetDeadline(time.Now().Add(time.Second))
+				_, _ = c.Write([]byte("It is a mistake to think you can solve any major problems just with potatoes.\n"))
 				c.Close()
 			}()
 		}
diff --git a/testing/http_example_test.go b/testing/http_example_test.go
index ea8b190..a89c944 100644
--- a/testing/http_example_test.go
+++ b/testing/http_example_test.go
@@ -94,5 +94,5 @@ func Example_httpShutdown() {
 	})
 
 	// Wait for connections to drain.
-	server.Shutdown(context.Background())
+	_ = server.Shutdown(context.Background())
 }
diff --git a/upgrader.go b/upgrader.go
index 59e0afe..9b5d5d6 100644
--- a/upgrader.go
+++ b/upgrader.go
@@ -263,11 +263,15 @@ func (u *Upgrader) doUpgrade() (*os.File, error) {
 			return nil, fmt.Errorf("child %s exited: %s", child, err)
 
 		case <-u.stopC:
-			child.Kill()
+			if err = child.Kill(); err != nil {
+				return nil, fmt.Errorf("terminating child: %w", err)
+			}
 			return nil, errors.New("terminating")
 
 		case <-readyTimeout:
-			child.Kill()
+			if err = child.Kill(); err != nil {
+				return nil, fmt.Errorf("terminating child: %w", err)
+			}
 			return nil, fmt.Errorf("new child %s timed out", child)
 
 		case file := <-child.ready:
diff --git a/upgrader_test.go b/upgrader_test.go
index dc724f7..acb21d3 100644
--- a/upgrader_test.go
+++ b/upgrader_test.go
@@ -137,7 +137,7 @@ func childProcess(upg *Upgrader) error {
 	// error here won't make the parent fail, so don't bother.
 	if rExit != nil {
 		var b [1]byte
-		rExit.Read(b[:])
+		_, _ = rExit.Read(b[:])
 	}
 
 	return nil