diff --git a/lib/srfi/231.sld b/lib/srfi/231.sld
index 3111f403..f3fad65f 100644
--- a/lib/srfi/231.sld
+++ b/lib/srfi/231.sld
@@ -33,6 +33,7 @@
    u64-storage-class f8-storage-class f16-storage-class
    f32-storage-class f64-storage-class
    c64-storage-class c128-storage-class
+   char-storage-class
    storage-class-data? storage-class-data->body
    ;; Arrays
    make-array array? array-domain array-getter array-dimension
diff --git a/lib/srfi/231/base.scm b/lib/srfi/231/base.scm
index ef129fbf..e4a3d0c5 100644
--- a/lib/srfi/231/base.scm
+++ b/lib/srfi/231/base.scm
@@ -117,10 +117,12 @@
          (vector-every < i (interval-ub iv)))))
 
 (define (interval-projections iv rd)
-  (values (make-interval (vector-copy (interval-lb iv) 0 rd)
-                         (vector-copy (interval-ub iv) 0 rd))
-          (make-interval (vector-copy (interval-lb iv) rd)
-                         (vector-copy (interval-ub iv) rd))))
+  (assert (interval? iv))
+  (let ((n (vector-length (interval-lb iv))))
+    (values (make-interval (vector-copy (interval-lb iv) 0 (- n rd))
+                           (vector-copy (interval-ub iv) 0 (- n rd)))
+            (make-interval (vector-copy (interval-lb iv) (- n rd))
+                           (vector-copy (interval-ub iv) (- n rd))))))
 
 (define (rev-index-next! rev-index rev-lowers rev-uppers)
   (cond