diff --git a/racket/collects/racket/private/unit-compiletime.rkt b/racket/collects/racket/private/unit-compiletime.rkt
index 343e71619a..8de0501209 100644
--- a/racket/collects/racket/private/unit-compiletime.rkt
+++ b/racket/collects/racket/private/unit-compiletime.rkt
@@ -598,6 +598,8 @@
 
 ;; This utility function returns a list of natural numbers for use as a syntax
 ;; property needed to support units in Typed Racket
+;; Each number in the list is an index into a unit's list of imports signifying
+;; that the import at that index is also an init-dependency of the unit
 (define (build-init-depend-property init-depends imports)
   (define (sig=? s1 s2)
     (and (eq? (syntax-e (car s1)) (car s2))
diff --git a/racket/collects/racket/unit.rkt b/racket/collects/racket/unit.rkt
index 65c18bf01f..ba6ae8dac6 100644
--- a/racket/collects/racket/unit.rkt
+++ b/racket/collects/racket/unit.rkt
@@ -1645,6 +1645,10 @@
                            (syntax->list #'((((sub-in-key sub-in-code) ...) ...) ...))))
                          )
              (values
+              ;; Attach a syntax-property containing indices of init-depends signatures
+              ;; for this compound unit. Although this property is attached to all
+              ;; compound-units, it is only meaningful when the compound unit was
+              ;; created via compound-unit/infer
               (syntax-property
                (quasisyntax/loc (error-syntax)
                  (let ([deps '()]