diff --git a/collects/scheme/private/string.ss b/collects/scheme/private/string.ss
index 0d04dcaeab..9e4cd7ec5a 100644
--- a/collects/scheme/private/string.ss
+++ b/collects/scheme/private/string.ss
@@ -15,18 +15,21 @@
   (define (real->decimal-string n [digits 2])
     (unless (exact-nonnegative-integer? digits)
       (raise-type-error 'real->decimal-string "exact-nonnegative-integer" n))
-    (if (zero? digits)
-      (number->string (inexact->exact (round n)))
-      (let* ([e (expt 10 digits)]
-             [num (round (abs (* e (inexact->exact n))))])
-        (format "~a~a.~a"
-                (if (negative? n) "-" "")
-                (quotient num e)
-                (let ([s (number->string (remainder num e))])
-                  (if (= (string-length s) digits)
-                    s
-                    (string-append (make-string (- digits (string-length s)) #\0)
-                                   s)))))))
+    (let* ([e (expt 10 digits)]
+           [num (round (abs (* e (inexact->exact n))))])
+      (format "~a~a.~a"
+              (if (or (negative? n) 
+                      (equal? n -0.0))
+                  "-" 
+                  "")
+              (quotient num e)
+              (if (zero? digits)
+                  ""
+                  (let ([s (number->string (remainder num e))])
+                    (if (= (string-length s) digits)
+                        s
+                        (string-append (make-string (- digits (string-length s)) #\0)
+                                       s)))))))
 
   ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;; Regexp helpers
diff --git a/collects/tests/mzscheme/string.ss b/collects/tests/mzscheme/string.ss
index 816fe94760..065ea72573 100644
--- a/collects/tests/mzscheme/string.ss
+++ b/collects/tests/mzscheme/string.ss
@@ -5,20 +5,21 @@
 
 ;; to add when this library is there: (require scheme/string)
 
-(test "0" real->decimal-string 0 0)
-(test "0" real->decimal-string 0.0 0)
-(test "1" real->decimal-string 0.6 0)
-(test "1" real->decimal-string 3/4 0)
-(test "1" real->decimal-string 1.2 0)
-(test "0" real->decimal-string -0.0 0) ; note this!
-(test "0.00" real->decimal-string -0.0) ; same here...
-(test "-1" real->decimal-string -0.6 0)
-(test "-1" real->decimal-string -3/4 0)
-(test "-1" real->decimal-string -1.2 0)
+(test "0." real->decimal-string 0 0)
+(test "0." real->decimal-string 0.0 0)
+(test "1." real->decimal-string 0.6 0)
+(test "1." real->decimal-string 3/4 0)
+(test "1." real->decimal-string 1.2 0)
+(test "-0." real->decimal-string -0.0 0) ; note this!
+(test "-0.00" real->decimal-string -0.0) ; same here...
+(test "-1." real->decimal-string -0.6 0)
+(test "-1." real->decimal-string -3/4 0)
+(test "-1." real->decimal-string -1.2 0)
 (test "1.20" real->decimal-string 1.2)
 (test "-1.20" real->decimal-string -1.2)
 (test "1.00" real->decimal-string 0.99999999999)
 (test "-1.00" real->decimal-string -0.99999999999)
+(test "1999999999999999859514578049071102439861518336.00" real->decimal-string 2e45)
 
 (let ([s (list->string
 	  (let loop ([i 0])