diff --git a/bin/migrations/builder_migrations.ml b/bin/migrations/builder_migrations.ml
index 88e53fe..e72ab39 100644
--- a/bin/migrations/builder_migrations.ml
+++ b/bin/migrations/builder_migrations.ml
@@ -90,6 +90,11 @@ let m20210218 =
   Cmdliner.Term.(const do_database_action $ const M20210218.migrate $ setup_log $ dbpath),
   Cmdliner.Term.info ~doc "migrate-2021-02-18"
 
+let r20210218 =
+  let doc = "Roll back column 'size' in 'build_file' and 'build_artifact' (2021-02-18)" in
+  Cmdliner.Term.(const do_database_action $ const M20210218.rollback $ setup_log $ dbpath),
+  Cmdliner.Term.info ~doc "rollback-2021-02-18"
+
 let help_cmd =
   let topic =
     let doc = "Migration to get help on" in
@@ -111,6 +116,6 @@ let () =
       m20210126; r20210126;
       m20210202; r20210202;
       m20210216; r20210216;
-      m20210218;
+      m20210218; r20210218;
     ]
   |> Cmdliner.Term.exit
diff --git a/bin/migrations/m20210218.ml b/bin/migrations/m20210218.ml
index 50d46dd..1229dcd 100644
--- a/bin/migrations/m20210218.ml
+++ b/bin/migrations/m20210218.ml
@@ -119,4 +119,61 @@ let migrate (module Db : Caqti_blocking.CONNECTION) =
 
     Db.exec (set_version new_user_version) ()
 
-(* FIXME: rollback. Requires copying data and creating new table without size column. *)
+let old_build_artifact =
+  Caqti_request.exec ~oneshot:true
+    Caqti_type.unit
+    {| CREATE TABLE new_build_artifact (
+           id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+           filepath TEXT NOT NULL, -- the path as in the build
+           localpath TEXT NOT NULL, -- local path to the file on disk
+           sha256 BLOB NOT NULL,
+           build INTEGER NOT NULL,
+
+           FOREIGN KEY(build) REFERENCES build(id),
+           UNIQUE(build, filepath)
+         )
+      |}
+
+let old_build_file =
+  Caqti_request.exec ~oneshot:true
+    Caqti_type.unit
+    {| CREATE TABLE new_build_file (
+           id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
+           filepath TEXT NOT NULL, -- the path as in the build
+           localpath TEXT NOT NULL, -- local path to the file on disk
+           sha256 BLOB NOT NULL,
+           build INTEGER NOT NULL,
+
+           FOREIGN KEY(build) REFERENCES build(id),
+           UNIQUE(build, filepath)
+         )
+      |}
+
+let copy_build_artifact =
+  Caqti_request.exec ~oneshot:true
+    Caqti_type.unit
+    "INSERT INTO new_build_artifact SELECT id, filepath, localpath, sha256, build FROM build_artifact"
+
+let copy_build_file =
+  Caqti_request.exec ~oneshot:true
+    Caqti_type.unit
+    "INSERT INTO new_build_file SELECT id, filepath, localpath, sha256, build FROM build_file"
+
+let rollback (module Db : Caqti_blocking.CONNECTION) =
+  let open Rresult.R.Infix in
+  Db.find Builder_db.get_application_id () >>= fun application_id ->
+  Db.find Builder_db.get_version () >>= fun user_version ->
+  if application_id <> Builder_db.application_id || user_version <> new_user_version
+  then Error (`Wrong_version (application_id, user_version))
+  else
+    Db.exec old_build_artifact () >>= fun () ->
+    Db.exec copy_build_artifact () >>= fun () ->
+    Db.exec drop_build_artifact () >>= fun () ->
+    Db.exec rename_build_artifact () >>= fun () ->
+
+    Db.exec old_build_file () >>= fun () ->
+    Db.exec copy_build_file () >>= fun () ->
+    Db.exec drop_build_file () >>= fun () ->
+    Db.exec rename_build_file () >>= fun () ->
+
+    Db.exec (set_version old_user_version) ()