diff --git a/atc/worker/gclient/factory.go b/atc/worker/gclient/factory.go
index 40cf90ef1..1fc6a3b9b 100644
--- a/atc/worker/gclient/factory.go
+++ b/atc/worker/gclient/factory.go
@@ -1,6 +1,7 @@
 package gclient
 
 import (
+	"fmt"
 	"net/http"
 	"time"
 
@@ -12,6 +13,10 @@ import (
 	"github.com/tedsuo/rata"
 )
 
+// Allows tests to override http.DefaultTransport's IdleConnTimeout. Only
+// applies to BasicGardenClientWithRequestTimeout.
+var idleConnTimeoutOverride string
+
 type gardenClientFactory struct {
 	db                         transport.TransportDB
 	logger                     lager.Logger
@@ -73,8 +78,18 @@ func (gcf *gardenClientFactory) NewClient() Client {
 
 // Do not try any client method that requires hijack functionality (streaming logs)!
 func BasicGardenClientWithRequestTimeout(logger lager.Logger, requestTimeout time.Duration, address string) Client {
+	httpTransport := http.DefaultTransport.(*http.Transport).Clone()
+	if idleConnTimeoutOverride != "" {
+		timeout, err := time.ParseDuration(idleConnTimeoutOverride)
+		if err != nil {
+			panic(fmt.Sprintf("invalid idleConnTimeoutOverride: %v", err))
+		}
+		httpTransport.IdleConnTimeout = timeout
+	}
+
 	streamClient := &http.Client{
-		Timeout: requestTimeout,
+		Transport: httpTransport,
+		Timeout:   requestTimeout,
 	}
 
 	streamer := &transport.WorkerHijackStreamer{
diff --git a/tsa/cmd/tsa/register_test.go b/tsa/cmd/tsa/register_test.go
index 86084514f..887af5d78 100644
--- a/tsa/cmd/tsa/register_test.go
+++ b/tsa/cmd/tsa/register_test.go
@@ -433,13 +433,20 @@ var _ = Describe("Register", func() {
 				Expect(res.StatusCode).To(Equal(http.StatusTeapot))
 
 				By("exiting successfully")
-				// https://golang.org/src/net/http/transport.go -> IdleConnTimeout is 90s in the DefaultTransport used by gclient.BasicGardenClientWithRequestTimeout
-				Eventually(registerErr, time.Second*100).Should(Receive(BeNil()))
+				// If this starts failing, it may be because we are no longer
+				// properly setting atc/worker/gclient.idleConnTimeoutOverride
+				// in the test binary. It defaults to 90s, which is incredibly
+				// slow for these tests.
+				Eventually(registerErr, time.Second*10).Should(Receive(BeNil()))
 			})
 
 			Context("with a drain timeout", func() {
 				BeforeEach(func() {
-					opts.ConnectionDrainTimeout = 5 * time.Second
+					// Note: this must not be "too close" to the idleConnTimeoutOverride
+					// value of 5s - otherwise, these timeouts seem to compound
+					// (e.g. if the drain timeout was also 5s, the effective
+					// timeout would be ~10s). Not too sure why this is
+					opts.ConnectionDrainTimeout = 3 * time.Second
 				})
 
 				It("breaks connections after the configured drain timeout", func() {
diff --git a/tsa/cmd/tsa/suite_test.go b/tsa/cmd/tsa/suite_test.go
index b518db033..6028e7523 100644
--- a/tsa/cmd/tsa/suite_test.go
+++ b/tsa/cmd/tsa/suite_test.go
@@ -39,7 +39,7 @@ var tsaPath string
 
 var _ = BeforeSuite(func() {
 	var err error
-	tsaPath, err = gexec.Build("github.com/concourse/concourse/tsa/cmd/tsa")
+	tsaPath, err = gexec.Build("github.com/concourse/concourse/tsa/cmd/tsa", "-ldflags", "-X 'github.com/concourse/concourse/atc/worker/gclient.idleConnTimeoutOverride=5s'")
 	Expect(err).NotTo(HaveOccurred())
 })