diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-container.scm
index cd71239527..dd56a79232 100644
--- a/gnu/build/linux-container.scm
+++ b/gnu/build/linux-container.scm
@@ -235,6 +235,8 @@ (define (run-container root mounts namespaces host-uids thunk)
                                                                namespaces)))
                     (lambda args
                       ;; Forward the exception to the parent process.
+                      ;; FIXME: SRFI-35 conditions and non-trivial objects
+                      ;; cannot be 'read' so they shouldn't be written as is.
                       (write args child)
                       (primitive-exit 3))))
                 ;; TODO: Manage capabilities.