diff --git a/lib/parse.ml b/lib/parse.ml
index 3c822d2..d513fe9 100644
--- a/lib/parse.ml
+++ b/lib/parse.ml
@@ -333,6 +333,12 @@ and form f mk (head : Form.t) (args : Form.t list) : Ast.expr =
            the restart stack without committing to one. *)
         | "find-restart" | "compute-restarts"
         | "errdefer" | "with-allocator" | "loop" | "recur"
+        (* plan.org's loop story is settled as imperative while/for with these
+           two and [return]. Neither exists, and both *alter control flow* —
+           the first thing the house rule says must be recognised explicitly.
+           Falling through to Call answered "unknown function break", which
+           reads as a typo rather than as a missing feature. *)
+        | "break" | "continue"
         | "await" as name) ->
     fail f "%s is not implemented yet (see the build sequence in plan.org)" name