diff --git a/docs/devel/api_changes.md b/docs/devel/api_changes.md
index be02e16c14d..d68a776fd75 100644
--- a/docs/devel/api_changes.md
+++ b/docs/devel/api_changes.md
@@ -236,7 +236,9 @@ assumptions.  If you have added any fields which need very careful formatting
 "this slice will always have at least 1 element", you may get an error or even
 a panic from the `serialization_test`.  If so, look at the diff it produces (or
 the backtrace in case of a panic) and figure out what you forgot.  Encode that
-into the fuzzer's custom fuzz functions.
+into the fuzzer's custom fuzz functions.  Hint: if you added defaults for a field,
+that field will need to have a custom fuzz function that ensures that the field is
+fuzzed to a non-empty value. 
 
 The fuzzer can be found in `pkg/api/testing/fuzzer.go`.