diff --git a/src/racket/src/resolve.c b/src/racket/src/resolve.c
index dbcd05e7ca..5fdedd2382 100644
--- a/src/racket/src/resolve.c
+++ b/src/racket/src/resolve.c
@@ -1933,7 +1933,7 @@ resolve_closure_compilation(Scheme_Object *_data, Resolve_Info *info,
           if (!convert_boxes)
             convert_boxes = allocate_boxmap(offset);
           scheme_boxmap_set(convert_boxes, cp, bit, 0);
-          if (need_flags)
+          if (need_flags && (bit > CLOS_TYPE_TYPE_OFFSET))
             scheme_boxmap_set(closure_map, cp + data->num_params, bit, need_flags);
         }
         closure_map[cp] = old_pos;
diff --git a/src/racket/src/schvers.h b/src/racket/src/schvers.h
index d164db2cdd..1aca10f549 100644
--- a/src/racket/src/schvers.h
+++ b/src/racket/src/schvers.h
@@ -13,12 +13,12 @@
    consistently.)
 */
 
-#define MZSCHEME_VERSION "5.3.1.7"
+#define MZSCHEME_VERSION "5.3.1.8"
 
 #define MZSCHEME_VERSION_X 5
 #define MZSCHEME_VERSION_Y 3
 #define MZSCHEME_VERSION_Z 1
-#define MZSCHEME_VERSION_W 7
+#define MZSCHEME_VERSION_W 8
 
 #define MZSCHEME_VERSION_MAJOR ((MZSCHEME_VERSION_X * 100) + MZSCHEME_VERSION_Y)
 #define MZSCHEME_VERSION_MINOR ((MZSCHEME_VERSION_Z * 1000) + MZSCHEME_VERSION_W)
diff --git a/src/racket/src/validate.c b/src/racket/src/validate.c
index d6d1a4d734..ac2019109b 100644
--- a/src/racket/src/validate.c
+++ b/src/racket/src/validate.c
@@ -1029,6 +1029,8 @@ static void validate_unclosed_procedure(Mz_CPort *port, Scheme_Object *expr,
       int pos = data->num_params + i;
       int ct;
       ct = scheme_boxmap_get(map, pos, data->closure_size);
+      if (ct == CLOS_TYPE_BOXED)
+        scheme_ill_formed_code(port);
       if (ct > CLOS_TYPE_TYPE_OFFSET) {
         if (vld != (VALID_TYPED + (ct - CLOS_TYPE_TYPE_OFFSET)))
           vld = VALID_NOT;