diff --git a/h2quic/client.go b/h2quic/client.go
index fd7eb85ef..c712915a3 100644
--- a/h2quic/client.go
+++ b/h2quic/client.go
@@ -168,8 +168,7 @@ func (c *Client) Do(req *http.Request) (*http.Response, error) {
 		c.cryptoChangedCond.Wait()
 	}
 	hdrChan := make(chan *http.Response)
-	// TODO: think about what to do with a TooManyOpenStreams error. Wait and retry?
-	dataStream, err := c.session.OpenStream()
+	dataStream, err := c.session.OpenStreamSync()
 	if err != nil {
 		c.Close(err)
 		return nil, err
diff --git a/h2quic/client_test.go b/h2quic/client_test.go
index 24b826698..c2eeaae02 100644
--- a/h2quic/client_test.go
+++ b/h2quic/client_test.go
@@ -181,6 +181,21 @@ var _ = Describe("Client", func() {
 			Expect(client.session.(*mockSession).closedWithError).To(MatchError(client.headerErr))
 		})
 
+		It("blocks if no stream is available", func() {
+			session.blockOpenStreamSync = true
+			var doReturned bool
+			go func() {
+				defer GinkgoRecover()
+				_, err := client.Do(request)
+				Expect(err).ToNot(HaveOccurred())
+				doReturned = true
+			}()
+			headerStream.dataToRead.Write([]byte("invalid response"))
+			go client.handleHeaderStream()
+
+			Consistently(func() bool { return doReturned }).Should(BeFalse())
+		})
+
 		Context("validating the address", func() {
 			It("refuses to do requests for the wrong host", func() {
 				req, err := http.NewRequest("https", "https://quic.clemente.io:1336/foobar.html", nil)
diff --git a/h2quic/server_test.go b/h2quic/server_test.go
index f760c6e17..b1e30c01e 100644
--- a/h2quic/server_test.go
+++ b/h2quic/server_test.go
@@ -9,6 +9,7 @@ import (
 	"runtime"
 	"sync"
 	"syscall"
+	"time"
 
 	"golang.org/x/net/http2"
 	"golang.org/x/net/http2/hpack"
@@ -23,12 +24,13 @@ import (
 )
 
 type mockSession struct {
-	closed          bool
-	closedWithError error
-	dataStream      quic.Stream
-	streamToAccept  quic.Stream
-	streamToOpen    quic.Stream
-	streamOpenErr   error
+	closed              bool
+	closedWithError     error
+	dataStream          quic.Stream
+	streamToAccept      quic.Stream
+	streamToOpen        quic.Stream
+	blockOpenStreamSync bool
+	streamOpenErr       error
 }
 
 func (s *mockSession) GetOrOpenStream(id protocol.StreamID) (quic.Stream, error) {
@@ -44,7 +46,10 @@ func (s *mockSession) OpenStream() (quic.Stream, error) {
 	return s.streamToOpen, nil
 }
 func (s *mockSession) OpenStreamSync() (quic.Stream, error) {
-	panic("not implemented")
+	if s.blockOpenStreamSync {
+		time.Sleep(time.Hour)
+	}
+	return s.OpenStream()
 }
 func (s *mockSession) Close(e error) error {
 	s.closed = true