diff --git a/internal/musig2v040/README.md b/internal/musig2v040/README.md
new file mode 100644
index 000000000..bd248d267
--- /dev/null
+++ b/internal/musig2v040/README.md
@@ -0,0 +1,10 @@
+# MuSig2 v0.4.0
+
+This package contains an exact copy of the MuSig2 code as found in
+`github.com/btcsuite/btcec/v2/schnorr/musig2` at the tag `btcec/v2.2.2`.
+
+This corresponds to the [MuSig2 BIP specification version of
+`v0.4.0`](https://github.com/jonasnick/bips/blob/musig2/bip-musig2.mediawiki).
+
+We only keep this code here to allow implementing a backward compatible,
+versioned MuSig2 RPC.
diff --git a/internal/musig2/bench_test.go b/internal/musig2v040/bench_test.go
similarity index 99%
rename from internal/musig2/bench_test.go
rename to internal/musig2v040/bench_test.go
index 70d7e931c..21e014e2f 100644
--- a/internal/musig2/bench_test.go
+++ b/internal/musig2v040/bench_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
-package musig2
+package musig2v040
 
 import (
 	"encoding/hex"
diff --git a/internal/musig2/context.go b/internal/musig2v040/context.go
similarity index 99%
rename from internal/musig2/context.go
rename to internal/musig2v040/context.go
index 19cef34fa..b1701164c 100644
--- a/internal/musig2/context.go
+++ b/internal/musig2v040/context.go
@@ -1,6 +1,6 @@
 // Copyright (c) 2013-2022 The btcsuite developers
 
-package musig2
+package musig2v040
 
 import (
 	"fmt"
diff --git a/internal/musig2/keys.go b/internal/musig2v040/keys.go
similarity index 99%
rename from internal/musig2/keys.go
rename to internal/musig2v040/keys.go
index 9acdca367..9016f0b56 100644
--- a/internal/musig2/keys.go
+++ b/internal/musig2v040/keys.go
@@ -1,6 +1,6 @@
 // Copyright 2013-2022 The btcsuite developers
 
-package musig2
+package musig2v040
 
 import (
 	"bytes"
diff --git a/internal/musig2/musig2_test.go b/internal/musig2v040/musig2_test.go
similarity index 99%
rename from internal/musig2/musig2_test.go
rename to internal/musig2v040/musig2_test.go
index b38090908..fbd7f13ee 100644
--- a/internal/musig2/musig2_test.go
+++ b/internal/musig2v040/musig2_test.go
@@ -1,6 +1,6 @@
 // Copyright 2013-2022 The btcsuite developers
 
-package musig2
+package musig2v040
 
 import (
 	"bytes"
diff --git a/internal/musig2/nonces.go b/internal/musig2v040/nonces.go
similarity index 99%
rename from internal/musig2/nonces.go
rename to internal/musig2v040/nonces.go
index c989d7068..86ca68318 100644
--- a/internal/musig2/nonces.go
+++ b/internal/musig2v040/nonces.go
@@ -1,6 +1,6 @@
 // Copyright 2013-2022 The btcsuite developers
 
-package musig2
+package musig2v040
 
 import (
 	"bytes"
diff --git a/internal/musig2/sign.go b/internal/musig2v040/sign.go
similarity index 99%
rename from internal/musig2/sign.go
rename to internal/musig2v040/sign.go
index b100dabf2..b1236c3a9 100644
--- a/internal/musig2/sign.go
+++ b/internal/musig2v040/sign.go
@@ -1,6 +1,6 @@
 // Copyright 2013-2022 The btcsuite developers
 
-package musig2
+package musig2v040
 
 import (
 	"bytes"