diff --git a/collects/typed-scheme/ts-reference.scrbl b/collects/typed-scheme/ts-reference.scrbl
index 824ff0466b..f52c4a9804 100644
--- a/collects/typed-scheme/ts-reference.scrbl
+++ b/collects/typed-scheme/ts-reference.scrbl
@@ -258,7 +258,8 @@ Scheme.
 @index["opaque"]{The fourth case} defines a new type @scheme[t].  @scheme[pred], imported from
 module @scheme[m], is a predicate for this type.  The type is defined
 as precisely those values to which @scheme[pred] produces
-@scheme[#t].  @scheme[pred] must have type @scheme[(Any -> Boolean)].
+@scheme[#t].  @scheme[pred] must have type @scheme[(Any -> Boolean)].  
+Opaque types must be required lexically before they are used.
 
 In all cases, the identifiers are protected with @rtech{contracts} which
 enforce the specified types.  If this contract fails, the module
diff --git a/collects/typed-scheme/typecheck/tc-structs.ss b/collects/typed-scheme/typecheck/tc-structs.ss
index 47bcd92a23..d1d37b38d8 100644
--- a/collects/typed-scheme/typecheck/tc-structs.ss
+++ b/collects/typed-scheme/typecheck/tc-structs.ss
@@ -51,7 +51,7 @@
   (syntax-case nm/par ()
     [nm (identifier? #'nm) (values #'nm #f #f (syntax-e #'nm) (make-F (syntax-e #'nm)))]
     [(nm par) (let* ([parent0 (parse-type #'par)]
-                     [parent (resolve-name parent0)])
+                     [parent (if (Name? parent0) (resolve-name parent0) (tc-error/stx #'par "parent type not a valid structure name: ~a" (syntax->datum #'par)))])
                 (values #'nm parent0 parent (syntax-e #'nm) (make-F (syntax-e #'nm))))]
     [_ (int-err "not a parent: ~a" (syntax->datum nm/par))]))