diff --git a/cmd/dendrite-demo-libp2p/main.go b/cmd/dendrite-demo-libp2p/main.go
index 7333e8b44..93d54f21c 100644
--- a/cmd/dendrite-demo-libp2p/main.go
+++ b/cmd/dendrite-demo-libp2p/main.go
@@ -75,7 +75,8 @@ func createFederationClient(
 		p2phttp.NewTransport(base.LibP2P, p2phttp.ProtocolOption("/matrix")),
 	)
 	return gomatrixserverlib.NewFederationClientWithTransport(
-		base.Base.Cfg.Matrix.ServerName, base.Base.Cfg.Matrix.KeyID, base.Base.Cfg.Matrix.PrivateKey, tr,
+		base.Base.Cfg.Matrix.ServerName, base.Base.Cfg.Matrix.KeyID,
+		base.Base.Cfg.Matrix.PrivateKey, true, tr,
 	)
 }
 
@@ -87,7 +88,7 @@ func createClient(
 		"matrix",
 		p2phttp.NewTransport(base.LibP2P, p2phttp.ProtocolOption("/matrix")),
 	)
-	return gomatrixserverlib.NewClientWithTransport(tr)
+	return gomatrixserverlib.NewClientWithTransport(true, tr)
 }
 
 func main() {
diff --git a/cmd/dendrite-demo-yggdrasil/yggconn/client.go b/cmd/dendrite-demo-yggdrasil/yggconn/client.go
index 56afe264d..9cb6f9756 100644
--- a/cmd/dendrite-demo-yggdrasil/yggconn/client.go
+++ b/cmd/dendrite-demo-yggdrasil/yggconn/client.go
@@ -33,7 +33,7 @@ func (n *Node) CreateClient(
 			},
 		},
 	)
-	return gomatrixserverlib.NewClientWithTransport(tr)
+	return gomatrixserverlib.NewClientWithTransport(true, tr)
 }
 
 func (n *Node) CreateFederationClient(
@@ -54,6 +54,7 @@ func (n *Node) CreateFederationClient(
 		},
 	)
 	return gomatrixserverlib.NewFederationClientWithTransport(
-		base.Cfg.Matrix.ServerName, base.Cfg.Matrix.KeyID, base.Cfg.Matrix.PrivateKey, tr,
+		base.Cfg.Matrix.ServerName, base.Cfg.Matrix.KeyID,
+		base.Cfg.Matrix.PrivateKey, true, tr,
 	)
 }
diff --git a/cmd/dendrite-media-api-server/main.go b/cmd/dendrite-media-api-server/main.go
index 1582a33a8..2b9c50902 100644
--- a/cmd/dendrite-media-api-server/main.go
+++ b/cmd/dendrite-media-api-server/main.go
@@ -26,7 +26,7 @@ func main() {
 	defer base.Close() // nolint: errcheck
 
 	userAPI := base.UserAPIClient()
-	client := gomatrixserverlib.NewClient()
+	client := gomatrixserverlib.NewClient(cfg.Matrix.FederationDisableTLSValidation)
 
 	mediaapi.AddPublicRoutes(base.PublicAPIMux, base.Cfg, userAPI, client)
 
diff --git a/cmd/dendrite-monolith-server/main.go b/cmd/dendrite-monolith-server/main.go
index c75ef8fbb..ed30685b8 100644
--- a/cmd/dendrite-monolith-server/main.go
+++ b/cmd/dendrite-monolith-server/main.go
@@ -126,7 +126,7 @@ func main() {
 		Config:        base.Cfg,
 		AccountDB:     accountDB,
 		DeviceDB:      deviceDB,
-		Client:        gomatrixserverlib.NewClient(),
+		Client:        gomatrixserverlib.NewClient(cfg.Matrix.FederationDisableTLSValidation),
 		FedClient:     federation,
 		KeyRing:       keyRing,
 		KafkaConsumer: base.KafkaConsumer,
diff --git a/cmd/dendritejs/main.go b/cmd/dendritejs/main.go
index fd407e6ed..274d170e4 100644
--- a/cmd/dendritejs/main.go
+++ b/cmd/dendritejs/main.go
@@ -139,16 +139,16 @@ func createFederationClient(cfg *config.Dendrite, node *go_http_js_libp2p.P2pLoc
 	tr := go_http_js_libp2p.NewP2pTransport(node)
 
 	fed := gomatrixserverlib.NewFederationClient(
-		cfg.Matrix.ServerName, cfg.Matrix.KeyID, cfg.Matrix.PrivateKey,
+		cfg.Matrix.ServerName, cfg.Matrix.KeyID, cfg.Matrix.PrivateKey, true,
 	)
-	fed.Client = *gomatrixserverlib.NewClientWithTransport(tr)
+	fed.Client = *gomatrixserverlib.NewClientWithTransport(true, tr)
 
 	return fed
 }
 
 func createClient(node *go_http_js_libp2p.P2pLocalNode) *gomatrixserverlib.Client {
 	tr := go_http_js_libp2p.NewP2pTransport(node)
-	return gomatrixserverlib.NewClientWithTransport(tr)
+	return gomatrixserverlib.NewClientWithTransport(true, tr)
 }
 
 func createP2PNode(privKey ed25519.PrivateKey) (serverName string, node *go_http_js_libp2p.P2pLocalNode) {
diff --git a/dendrite-config.yaml b/dendrite-config.yaml
index 8a0ecdaed..8f1448754 100644
--- a/dendrite-config.yaml
+++ b/dendrite-config.yaml
@@ -27,6 +27,9 @@ matrix:
     #        public_key: l8Hft5qXKn1vfHrg3p4+W8gELQVo8N13JkluMfmn2sQ
     # Disables new users from registering (except via shared secrets)
     registration_disabled: false
+    # Whether to disable TLS certificate validation. Warning: this reduces federation
+    # security and should not be enabled in production!
+    federation_disable_tls_validation: false
 
 # The media repository config
 media:
diff --git a/federationapi/federationapi_test.go b/federationapi/federationapi_test.go
index 8bc4277eb..0e0d77409 100644
--- a/federationapi/federationapi_test.go
+++ b/federationapi/federationapi_test.go
@@ -43,7 +43,7 @@ func TestRoomsV3URLEscapeDoNot404(t *testing.T) {
 	defer cancel()
 	serverName := gomatrixserverlib.ServerName(strings.TrimPrefix(baseURL, "https://"))
 
-	fedCli := gomatrixserverlib.NewFederationClient(serverName, cfg.Matrix.KeyID, cfg.Matrix.PrivateKey)
+	fedCli := gomatrixserverlib.NewFederationClient(serverName, cfg.Matrix.KeyID, cfg.Matrix.PrivateKey, true)
 
 	testCases := []struct {
 		roomVer   gomatrixserverlib.RoomVersion
diff --git a/go.mod b/go.mod
index c35ae4b55..2f301e04d 100644
--- a/go.mod
+++ b/go.mod
@@ -21,7 +21,7 @@ require (
 	github.com/matrix-org/go-http-js-libp2p v0.0.0-20200518170932-783164aeeda4
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20200522092705-bc8506ccbcf3
 	github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20200807132727-7b8c09bcdfb2
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20200807145008-79c173b65786
 	github.com/matrix-org/naffka v0.0.0-20200422140631-181f1ee7401f
 	github.com/matrix-org/util v0.0.0-20200807132607-55161520e1d4
 	github.com/mattn/go-sqlite3 v2.0.2+incompatible
diff --git a/go.sum b/go.sum
index fa8f55546..bc3bb1951 100644
--- a/go.sum
+++ b/go.sum
@@ -421,8 +421,8 @@ github.com/matrix-org/go-sqlite3-js v0.0.0-20200522092705-bc8506ccbcf3 h1:Yb+Wlf
 github.com/matrix-org/go-sqlite3-js v0.0.0-20200522092705-bc8506ccbcf3/go.mod h1:e+cg2q7C7yE5QnAXgzo512tgFh1RbQLC0+jozuegKgo=
 github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26 h1:Hr3zjRsq2bhrnp3Ky1qgx/fzCtCALOoGYylh2tpS9K4=
 github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26/go.mod h1:3fxX6gUjWyI/2Bt7J1OLhpCzOfO/bB3AiX0cJtEKud0=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20200807132727-7b8c09bcdfb2 h1:3eJsj8uJcr/rrxuIAY+kkIYBJUOeJkzQ8Vb4juvddXU=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20200807132727-7b8c09bcdfb2/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200807145008-79c173b65786 h1:HQclx5J2CrCBqP88t5Di9IkVDJZn5+h4ZL48viY4FJ4=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200807145008-79c173b65786/go.mod h1:JsAzE1Ll3+gDWS9JSUHPJiiyAksvOOnGWF2nXdg4ZzU=
 github.com/matrix-org/naffka v0.0.0-20200422140631-181f1ee7401f h1:pRz4VTiRCO4zPlEMc3ESdUOcW4PXHH4Kj+YDz1XyE+Y=
 github.com/matrix-org/naffka v0.0.0-20200422140631-181f1ee7401f/go.mod h1:y0oDTjZDv5SM9a2rp3bl+CU+bvTRINQsdb7YlDql5Go=
 github.com/matrix-org/util v0.0.0-20190711121626-527ce5ddefc7 h1:ntrLa/8xVzeSs8vHFHK25k0C+NV74sYMJnNSg5NoSRo=
diff --git a/internal/config/config.go b/internal/config/config.go
index 657e804f6..900d3b14c 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -107,6 +107,9 @@ type Dendrite struct {
 		// is 2**x seconds, so 1 = 2 seconds, 2 = 4 seconds, 3 = 8 seconds, etc.
 		// The default value is 16 if not specified, which is circa 18 hours.
 		FederationMaxRetries uint32 `yaml:"federation_max_retries"`
+		// FederationDisableTLSValidation disables the validation of X.509 TLS certs
+		// on remote federation endpoints. This is not recommended in production!
+		FederationDisableTLSValidation bool `yaml:"federation_disable_tls_validation"`
 	} `yaml:"matrix"`
 
 	// The configuration specific to the media repostitory.
diff --git a/internal/setup/base.go b/internal/setup/base.go
index 333c01736..4fef0cbc8 100644
--- a/internal/setup/base.go
+++ b/internal/setup/base.go
@@ -252,6 +252,7 @@ func (b *BaseDendrite) CreateAccountsDB() accounts.Database {
 func (b *BaseDendrite) CreateFederationClient() *gomatrixserverlib.FederationClient {
 	return gomatrixserverlib.NewFederationClient(
 		b.Cfg.Matrix.ServerName, b.Cfg.Matrix.KeyID, b.Cfg.Matrix.PrivateKey,
+		b.Cfg.Matrix.FederationDisableTLSValidation,
 	)
 }
 
diff --git a/serverkeyapi/serverkeyapi_test.go b/serverkeyapi/serverkeyapi_test.go
index 3368f5b2a..c53575bb7 100644
--- a/serverkeyapi/serverkeyapi_test.go
+++ b/serverkeyapi/serverkeyapi_test.go
@@ -85,7 +85,7 @@ func TestMain(m *testing.M) {
 
 		// Create the federation client.
 		s.fedclient = gomatrixserverlib.NewFederationClientWithTransport(
-			s.config.Matrix.ServerName, serverKeyID, testPriv, transport,
+			s.config.Matrix.ServerName, serverKeyID, testPriv, true, transport,
 		)
 
 		// Finally, build the server key APIs.