diff --git a/src/crypto/tls/handshake_messages.go b/src/crypto/tls/handshake_messages.go
index 40c54cca58b..b3840f6c10f 100644
--- a/src/crypto/tls/handshake_messages.go
+++ b/src/crypto/tls/handshake_messages.go
@@ -248,7 +248,7 @@ func (m *clientHelloMsg) marshal() ([]byte, error) {
 			})
 		})
 	}
-	if len(m.keyShares) > 0 {
+	if m.keyShares != nil {
 		// RFC 8446, Section 4.2.8
 		exts.AddUint16(extensionKeyShare)
 		exts.AddUint16LengthPrefixed(func(exts *cryptobyte.Builder) {