diff --git a/client.go b/client.go
index be0b78c4f..1b6756407 100644
--- a/client.go
+++ b/client.go
@@ -6,6 +6,7 @@ import (
 	"math/rand"
 	"net"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/lucas-clemente/quic-go/protocol"
@@ -22,6 +23,7 @@ type Client struct {
 	connectionID      protocol.ConnectionID
 	version           protocol.VersionNumber
 	versionNegotiated bool
+	closed            uint32 // atomic bool
 
 	cryptoChangeCallback     CryptoChangeCallback
 	versionNegotiateCallback VersionNegotiateCallback
@@ -111,6 +113,11 @@ func (c *Client) OpenStream(id protocol.StreamID) (utils.Stream, error) {
 
 // Close closes the connection
 func (c *Client) Close(e error) error {
+	// Only close once
+	if !atomic.CompareAndSwapUint32(&c.closed, 0, 1) {
+		return nil
+	}
+
 	_ = c.session.Close(e)
 	return c.conn.Close()
 }
diff --git a/client_test.go b/client_test.go
index be2bb95eb..4941c30ed 100644
--- a/client_test.go
+++ b/client_test.go
@@ -77,11 +77,20 @@ var _ = Describe("Client", func() {
 		Expect(err).ToNot(HaveOccurred())
 		Eventually(session.closed).Should(BeTrue())
 		Expect(session.closeReason).To(MatchError(testErr))
+		Expect(client.closed).To(Equal(uint32(1)))
 		Eventually(func() bool { return stoppedListening }).Should(BeTrue())
 		Eventually(runtime.NumGoroutine()).Should(Equal(numGoRoutines))
 		close(done)
 	})
 
+	It("only closes the client once", func() {
+		client.closed = 1
+		err := client.Close(errors.New("test error"))
+		Expect(err).ToNot(HaveOccurred())
+		Eventually(session.closed).Should(BeFalse())
+		Expect(session.closeReason).ToNot(HaveOccurred())
+	})
+
 	It("creates new sessions with the right parameters", func() {
 		startUDPConn()
 		client.session = nil