diff --git a/docs/adr/001_design_principles.md b/docs/adr/001_design_principles.md
index 530aac2..a155ef9 100644
--- a/docs/adr/001_design_principles.md
+++ b/docs/adr/001_design_principles.md
@@ -25,7 +25,7 @@ To resolve this, I'm enforcing two new principles onto the contract of `go-cucko
 
 These principles should _guide_ the public interface of `go-cuckoo`.
 Neither should be treated absolutely, though.
-The behavior of `go-cuckoo` is distinct from `map`.
+The behavior of `go-cuckoo` is distinct from `map` (e.g. `Put` can fail; see `ErrBadHash`).
 Do not equate them.
 
 ## Consequences