diff --git a/doc/chibi.scrbl b/doc/chibi.scrbl
index 8865d4a3..a673c52b 100755
--- a/doc/chibi.scrbl
+++ b/doc/chibi.scrbl
@@ -156,13 +156,14 @@ currently unspecified.
 In R7RS (and R6RS) semantics it is impossible to use two macros from
 different modules which both use the same auxiliary keywords (like
 \scheme{else} in \scheme{cond} forms) without renaming one of the
-keywords.  By default Chibi considers all top-level bindings
-effectively unbound when matching auxiliary keywords, so this case
-will "just work".  This decision was made because the chance of
-different modules using the same keywords seems more likely than user
-code unintentionally matching a top-level keyword with a different
-binding, however if you want to use R7RS semantics you can compile
-with \ccode{SEXP_USE_STRICT_TOPLEVEL_BINDINGS=1}.
+keywords.  To minimize conflicts Chibi offers a special module named
+\scheme{(auto)} which can export any identifier requested with
+\scheme{only}, e.g. \scheme{(import (only (auto) foo))} will import
+an auxiliary syntax \scheme{foo} binding.  Separate modules can use
+this to get the same binding without needing to know about each other
+in advance.  This is a Chibi-specific extension so is non-portable, but
+you can always define a static \scheme{(auto)} module exporting a list
+of all known bindings for other implementations.
 
 \scheme{load} is extended to accept an optional environment argument, like
 \scheme{eval}.  You can also \scheme{load} shared libraries in addition to
@@ -1584,7 +1585,7 @@ command tells you which you currently have installed.  The following
 are currently supported:
 
 \itemlist[
-\item{chibi - native support as of version 0.7.3}
+\item{chibi - version >= 0.7.3}
 \item{chicken - version >= 4.9.0 with the \scheme{r7rs} egg}
 \item{cyclone - version >= 0.5.3}
 \item{foment - version >= 0.4}
diff --git a/lib/chibi/math/prime.scm b/lib/chibi/math/prime.scm
index 50775b40..23bac3a9 100644
--- a/lib/chibi/math/prime.scm
+++ b/lib/chibi/math/prime.scm
@@ -78,7 +78,7 @@
   ;; returns 1 modulo n.
   (let ((b (modular-expt a odd n)))
     (let lp ((i 0) (b b))
-      (cond ((or (= b 1) (= b neg1)))  ; in (= b 1) case we could factor
+      (cond ((or (= b 1) (= b neg1))) ; in (= b 1) case we could factor
             ((>= i twos) #f)
             (else (lp (+ i 1) (remainder (* b b) n)))))))
 
diff --git a/lib/chibi/math/prime.sld b/lib/chibi/math/prime.sld
index 9fbf433b..e0929f4d 100644
--- a/lib/chibi/math/prime.sld
+++ b/lib/chibi/math/prime.sld
@@ -10,5 +10,6 @@
           provable-prime? probable-prime?
           random-prime random-prime-distinct-from
           coprime? random-coprime modular-inverse modular-expt
-          miller-rabin-composite?)
+          miller-rabin-composite?
+          modular-root-of-one?)
   (include "prime.scm"))
diff --git a/lib/chibi/optional-test.sld b/lib/chibi/optional-test.sld
index 28fd68ac..9c1b56c6 100644
--- a/lib/chibi/optional-test.sld
+++ b/lib/chibi/optional-test.sld
@@ -53,6 +53,8 @@
       (test '(0 1 (2 3 4))
           (let-optionals '(0 1 2 3 4) ((a 10) (b 11) . c)
             (list a b c)))
+      (test 5 (keyword-ref '(a: b: b: 5) 'b: #f))
+      (test 5 (keyword-ref* '(a: b: b: 5) 'b: #f))
       (cond-expand
        (gauche)     ; gauche detects this at compile-time, can't catch
        (else (test-error '(0 11 12)
diff --git a/lib/chibi/optional.scm b/lib/chibi/optional.scm
index d703c737..7168d9dc 100644
--- a/lib/chibi/optional.scm
+++ b/lib/chibi/optional.scm
@@ -95,6 +95,13 @@
     ((define-opt (name . vars) . body)
      (define name (opt-lambda vars . body)))))
 
+(define (mem-key key ls)
+  (and (pair? ls)
+       (pair? (cdr ls))
+       (if (eq? key (car ls))
+           ls
+           (mem-key key (cddr ls)))))
+
 ;;> \procedure{(keyword-ref ls key [default])}
 ;;>
 ;;> Search for the identifier \var{key} in the list \var{ls}, treating
@@ -103,12 +110,8 @@
 ;;> \var{default}, or \scheme{#f}.
 
 (define (keyword-ref ls key . o)
-  (let lp ((ls ls))
-    (if (and (pair? ls) (pair? (cdr ls)))
-        (if (eq? key (car ls))
-            (cadr ls)
-            (lp (cddr ls)))
-        (and (pair? o) (car o)))))
+  (cond ((mem-key key ls) => (lambda (cell) (cadr cell)))
+        (else (and (pair? o) (car o)))))
 
 ;;> \macro{(keyword-ref* ls key default)}
 ;;>
@@ -118,7 +121,7 @@
 (define-syntax keyword-ref*
   (syntax-rules ()
     ((keyword-ref* ls key default)
-     (cond ((memq key ls) => cadr) (else default)))))
+     (cond ((mem-key key ls) => cadr) (else default)))))
 
 (define (symbol->keyword sym)
   (string->symbol (string-append (symbol->string sym) ":")))