diff --git a/lib/chibi/uri.scm b/lib/chibi/uri.scm
index d5cfbd5d..e59a611b 100644
--- a/lib/chibi/uri.scm
+++ b/lib/chibi/uri.scm
@@ -170,7 +170,7 @@
 (define (string->uri str . o)
   (apply string->path-uri #f str o))
 
-;;> Convert a URI object to a string.
+;;> Convert a URI object to a string.  Returns #f if the uri has no scheme.
 
 (define (uri->string uri . o)
   (define encode? (and (pair? o) (car o)))
@@ -194,6 +194,14 @@
          (if (pair? query) (uri-alist->query query) (or query ""))
          (if fragment "#" "") (if fragment (encode fragment) "")))))
 
+;;> Returns true iff the given URI string has a scheme.
+
+(define uri-has-scheme?
+  (let ((no-scheme (list 'no-scheme)))
+    (lambda (url)
+      (and url
+           (eq? no-scheme (uri-scheme (string->path-uri no-scheme url)))))))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; query encoding and decoding
 
diff --git a/lib/chibi/uri.sld b/lib/chibi/uri.sld
index 0494e351..1a7310fe 100644
--- a/lib/chibi/uri.sld
+++ b/lib/chibi/uri.sld
@@ -1,6 +1,6 @@
 
 (define-library (chibi uri)
-  (export uri? uri->string make-uri string->uri string->path-uri
+  (export uri? uri->string make-uri string->uri string->path-uri uri-has-scheme?
           uri-scheme uri-user uri-host uri-port uri-path uri-query uri-fragment
           uri-with-scheme uri-with-user uri-with-host uri-with-path
           uri-with-query uri-with-fragment