diff --git a/lib/chibi/regexp.scm b/lib/chibi/regexp.scm
index 72a99ac3..1c3092c1 100644
--- a/lib/chibi/regexp.scm
+++ b/lib/chibi/regexp.scm
@@ -45,6 +45,7 @@
 
 (define ~none 0)
 (define ~ci? 1)
+(define ~ascii? 2)
 
 (define (flag-set? flags i) (= i (bitwise-and flags i)))
 (define (flag-join a b) (if b (bitwise-ior a b) a))
@@ -194,7 +195,8 @@
    ((and (pair? md) (string-cursor? (car md)) (string-cursor? (cdr md)))
     (substring-cursor str (car md) (cdr md)))
    ((regexp-match? md)
-    (regexp-match-convert recurse? (regexp-match-matches md) (regexp-match-string md)))
+    (regexp-match-convert
+     recurse? (regexp-match-matches md) (regexp-match-string md)))
    (else
     md)))
 
@@ -245,15 +247,19 @@
       (cond
        ((>= i end)
         #t)
-       ((and (eqv? (regexp-match-ref m1 i) (regexp-match-ref m2 i))
-             (eqv? (regexp-match-ref m1 (+ i 1)) (regexp-match-ref m2 (+ i 1))))
+       ((and (eqv? (regexp-match-ref m1 i)
+                   (regexp-match-ref m2 i))
+             (eqv? (regexp-match-ref m1 (+ i 1))
+                   (regexp-match-ref m2 (+ i 1))))
         (lp (+ i 2)))
        ((and (string-cursor? (regexp-match-ref m2 i))
              (string-cursor? (regexp-match-ref m2 (+ i 1)))
              (or (not (string-cursor? (regexp-match-ref m1 i)))
                  (not (string-cursor? (regexp-match-ref m1 (+ i 1))))
-                 (string-cursor<? (regexp-match-ref m2 i) (regexp-match-ref m1 i))
-                 (and (string-cursor=? (regexp-match-ref m2 i) (regexp-match-ref m1 i))
+                 (string-cursor<? (regexp-match-ref m2 i)
+                                  (regexp-match-ref m1 i))
+                 (and (string-cursor=? (regexp-match-ref m2 i)
+                                       (regexp-match-ref m1 i))
                       (string-cursor>? (regexp-match-ref m2 (+ i 1))
                                        (regexp-match-ref m1 (+ i 1))))))
         #f)
@@ -469,6 +475,8 @@
 (define char-set:control (ucs-range->char-set 0 32))
 (define char-set:word-constituent
   (char-set-union char-set:letter char-set:digit (char-set #\_)))
+(define %char-set:word-constituent
+  (char-set-union %char-set:letter %char-set:digit (char-set #\_)))
 (define (char-word-constituent? ch)
   (char-set-contains? char-set:word-constituent ch))
 
@@ -529,26 +537,47 @@
              (match/bog str i2 ch2 start end matches)))))
 
 (define (lookup-char-set name flags)
-  (case name
-    ((any) char-set:full)
-    ((nonl) char-set:nonl)
-    ((lower-case lower)
-     (if (flag-set? flags ~ci?) char-set:letter char-set:lower-case))
-    ((upper-case upper)
-     (if (flag-set? flags ~ci?) char-set:letter char-set:upper-case))
-    ((alphabetic alpha) char-set:letter)
-    ((numeric num digit) char-set:digit)
-    ((alphanumeric alphanum alnum) char-set:letter+digit)
-    ((punctuation punct) char-set:punctuation)
-    ((graphic graph) char-set:graphic)
-    ((word-constituent) char-set:word-constituent)
-    ((whitespace white space) char-set:whitespace)
-    ((printing print) char-set:printing)
-    ((control cntrl) char-set:control)
-    ((hex-digit xdigit hex) char-set:hex-digit)
-    ((blank) char-set:blank)
-    ((ascii) char-set:ascii)
-    (else #f)))
+  (cond
+   ((flag-set? flags ~ascii?)
+    (case name
+      ((any) char-set:full)
+      ((nonl) char-set:nonl)
+      ((lower-case lower)
+       (if (flag-set? flags ~ci?) %char-set:letter %char-set:lower-case))
+      ((upper-case upper)
+       (if (flag-set? flags ~ci?) %char-set:letter %char-set:upper-case))
+      ((alphabetic alpha) %char-set:letter)
+      ((numeric num digit) %char-set:digit)
+      ((alphanumeric alphanum alnum) %char-set:letter+digit)
+      ((punctuation punct) %char-set:punctuation)
+      ((graphic graph) %char-set:graphic)
+      ((word-constituent) %char-set:word-constituent)
+      ((whitespace white space) %char-set:whitespace)
+      ((printing print) %char-set:printing)
+      ((control cntrl) %char-set:iso-control)
+      ((hex-digit xdigit hex) char-set:hex-digit)
+      ((ascii) char-set:ascii)
+      (else #f)))
+   (else
+    (case name
+      ((any) char-set:full)
+      ((nonl) char-set:nonl)
+      ((lower-case lower)
+       (if (flag-set? flags ~ci?) char-set:letter char-set:lower-case))
+      ((upper-case upper)
+       (if (flag-set? flags ~ci?) char-set:letter char-set:upper-case))
+      ((alphabetic alpha) char-set:letter)
+      ((numeric num digit) char-set:digit)
+      ((alphanumeric alphanum alnum) char-set:letter+digit)
+      ((punctuation punct) char-set:punctuation)
+      ((graphic graph) char-set:graphic)
+      ((word-constituent) char-set:word-constituent)
+      ((whitespace white space) char-set:whitespace)
+      ((printing print) char-set:printing)
+      ((control cntrl) char-set:control)
+      ((hex-digit xdigit hex) char-set:hex-digit)
+      ((ascii) char-set:ascii)
+      (else #f)))))
 
 (define (sre-flatten-ranges orig-ls)
   (let lp ((ls orig-ls) (res '()))
@@ -777,6 +806,10 @@
          (->rx `(: ,@(cdr sre)) (flag-clear flags ~ci?) next))
         ((w/nocase)
          (->rx `(: ,@(cdr sre)) (flag-join flags ~ci?) next))
+        ((w/unicode)
+         (->rx `(: ,@(cdr sre)) (flag-clear flags ~ascii?) next))
+        ((w/ascii)
+         (->rx `(: ,@(cdr sre)) (flag-join flags ~ascii?) next))
         (else
          (if (string? (car sre))
              (make-char-state (sre->char-set sre flags) ~none next)
diff --git a/lib/chibi/regexp.sld b/lib/chibi/regexp.sld
index ee68df38..ed1cb7ad 100644
--- a/lib/chibi/regexp.sld
+++ b/lib/chibi/regexp.sld
@@ -10,9 +10,32 @@
   ;; Chibi's char-set library is more factored than SRFI-14.
   (cond-expand
    (chibi
-    (import (chibi) (srfi 9) (chibi char-set) (chibi char-set full)))
+    (import (chibi) (srfi 9) (chibi char-set)
+            (chibi char-set full)
+            (prefix (chibi char-set ascii) %)))
    (else
-    (import (scheme base) (srfi 14))))
+    (import (scheme base) (srfi 14))
+    (begin
+      (define %char-set:letter
+        (char-set-intersection char-set:ascii char-set:letter))
+      (define %char-set:lower-case
+        (char-set-intersection char-set:ascii char-set:lower-case))
+      (define %char-set:upper-case
+        (char-set-intersection char-set:ascii char-set:upper-case))
+      (define %char-set:digit
+        (char-set-intersection char-set:ascii char-set:digit))
+      (define %char-set:letter+digit
+        (char-set-intersection char-set:ascii char-set:letter+digit))
+      (define %char-set:punctuation
+        (char-set-intersection char-set:ascii char-set:punctuation))
+      (define %char-set:graphic
+        (char-set-intersection char-set:ascii char-set:graphic))
+      (define %char-set:whitespace
+        (char-set-intersection char-set:ascii char-set:whitespace))
+      (define %char-set:printing
+        (char-set-intersection char-set:ascii char-set:printing))
+      (define %char-set:iso-control
+        (char-set-intersection char-set:ascii char-set:iso-control)))))
   (import (chibi char-set boundary))
   ;; Use string-cursors where available.
   (begin
diff --git a/tests/regexp-tests.scm b/tests/regexp-tests.scm
index 1447fd31..87bafb87 100644
--- a/tests/regexp-tests.scm
+++ b/tests/regexp-tests.scm
@@ -143,6 +143,12 @@
 (test-re #f '(* lower) "abcD")
 (test-re '("abcD") '(w/nocase (* lower)) "abcD")
 
+(test-re '("кириллица") '(* alpha) "кириллица")
+(test-re #f '(w/ascii (* alpha)) "кириллица")
+
+(test-re '("１２３４５") '(* digit) "１２３４５")
+(test-re #f '(w/ascii (* digit)) "１２３４５")
+
 (test-re '("한") 'grapheme "한")
 (test-re '("글") 'grapheme "글")