diff --git a/http3/server_test.go b/http3/server_test.go
index fdc882f9..eec52ad3 100644
--- a/http3/server_test.go
+++ b/http3/server_test.go
@@ -339,7 +339,7 @@ var _ = Describe("Server", func() {
 		}
 
 		BeforeEach(func() {
-			Expect(getExpectedHeader([]protocol.VersionNumber{99, 90, 9})).To(Equal(http.Header{"Alt-Svc": {nextProtoH3 + `=":443"; ma=2592000; quic="99,90,9"`}}))
+			Expect(getExpectedHeader([]protocol.VersionNumber{0x00000001, 0x1abadaba})).To(Equal(http.Header{"Alt-Svc": {nextProtoH3 + `=":443"; ma=2592000; quic="1,1abadaba"`}}))
 			expected = getExpectedHeader(protocol.SupportedVersions)
 		})
 
diff --git a/internal/protocol/version.go b/internal/protocol/version.go
index 3406cfa4..69ccbe48 100644
--- a/internal/protocol/version.go
+++ b/internal/protocol/version.go
@@ -50,7 +50,7 @@ func (vn VersionNumber) String() string {
 
 // ToAltSvc returns the representation of the version for the H2 Alt-Svc parameters
 func (vn VersionNumber) ToAltSvc() string {
-	return fmt.Sprintf("%d", vn)
+	return fmt.Sprintf("%x", uint32(vn))
 }
 
 func (vn VersionNumber) isGQUIC() bool {