diff --git a/proposals/XXXX-tofu.md b/proposals/3834-tofu.md
similarity index 95%
rename from proposals/XXXX-tofu.md
rename to proposals/3834-tofu.md
index 6afd60a39..15315bf6d 100644
--- a/proposals/XXXX-tofu.md
+++ b/proposals/3834-tofu.md
@@ -1,4 +1,4 @@
-# MSCXXXX: Opportunistic user key pinning (TOFU)
+# MSC3834: Opportunistic user key pinning (TOFU)
 
 In the Matrix spec at present, there are no real provisions for
 properly authenticating devices belonging to other users, aside from
@@ -104,13 +104,13 @@ is dropping messages.
 
 This proposal does not add any new API endpoints, but does add some
 new fields and message types to existing data structures. These field
-names and message types will be prefixed with `org.matrix.mscXXXX.v1`.
+names and message types will be prefixed with `org.matrix.msc3834.v1`.
 Test implementations can identify the TSK as
-`org.matrix.mscXXXX.v1.cross_signing.tofu_signing`, use the optional
-field `org.matrix.mscXXXX.v1.tofu_signing_key` for the
+`org.matrix.msc3834.v1.cross_signing.tofu_signing`, use the optional
+field `org.matrix.msc3834.v1.tofu_signing_key` for the
 `keys/device_signing/upload` endpoint, and use the message types
-`org.matrix.mscXXXX.v1.signatures_hash_request` and
-`org.matrix.mscXXXX.v1.signatures_hash` for exchanging hashes of the
+`org.matrix.msc3834.v1.signatures_hash_request` and
+`org.matrix.msc3834.v1.signatures_hash` for exchanging hashes of the
 set of cross-signing signatures.
 
 ## Migration notes