diff --git a/pkgs/racket-test-core/tests/racket/stx.rktl b/pkgs/racket-test-core/tests/racket/stx.rktl
index 838992b882..41232667cc 100644
--- a/pkgs/racket-test-core/tests/racket/stx.rktl
+++ b/pkgs/racket-test-core/tests/racket/stx.rktl
@@ -1814,6 +1814,18 @@
     (test #t free-identifier=? #'begin (syntax-case a-b-stx ()
                                          [(b . _) (datum->syntax #'b 'begin)]))))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; syntax-debug-info
+
+(let ([check (lambda (syntax-debug-info)
+               (test 'x hash-ref (syntax-debug-info #'x) 'name)
+               (test 'nope hash-ref (syntax-debug-info #'1) 'name 'nope)
+               (test 'nope hash-ref (syntax-debug-info #'(x y)) 'name 'nope))])
+  (check syntax-debug-info)
+  (parameterize ([current-namespace (make-base-namespace)])
+    (eval '(require (prefix-in foo: racket/base)))
+    (check (lambda (stx) (syntax-debug-info (namespace-syntax-introduce stx))))))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Check that attacks are thwarted via `syntax-local-get-shadower'
 ;; or `make-syntax-delta-introducer':
diff --git a/racket/src/racket/src/syntax.c b/racket/src/racket/src/syntax.c
index 62c5a8b0cb..1320cd5e22 100644
--- a/racket/src/racket/src/syntax.c
+++ b/racket/src/racket/src/syntax.c
@@ -4679,6 +4679,9 @@ static Scheme_Object *unmarshal_lookup_adjust(Scheme_Object *sym, Scheme_Object
   Scheme_Hash_Tree *excepts;
   Scheme_Object *prefix;
 
+  if (!SCHEME_SYMBOLP(sym))
+    return scheme_false;
+
   excepts = extract_unmarshal_excepts(SCHEME_VEC_ELS(pes)[3]);
   prefix = extract_unmarshal_prefix(SCHEME_VEC_ELS(pes)[3]);