diff --git a/module/srfi/srfi-19.scm b/module/srfi/srfi-19.scm
index 1b795f380..c6a55a253 100644
--- a/module/srfi/srfi-19.scm
+++ b/module/srfi/srfi-19.scm
@@ -1005,24 +1005,14 @@
                                       #\Space 2)
                         port)))
    (cons #\f (lambda (date pad-with port)
-               (if (> (date-nanosecond date)
-                      nano)
-                   (display (padding (+ (date-second date) 1)
-                                          pad-with 2)
-                            port)
-                   (display (padding (date-second date)
-                                          pad-with 2)
-                            port))
-               (receive (i f)
-                        (split-real (/
-                                          (date-nanosecond date)
-                                          nano 1.0))
-                        (let* ((ns (number->string f))
-                               (le (string-length ns)))
-                          (if (> le 2)
-                              (begin
-                                (display (locale-decimal-point) port)
-                                (display (substring ns 2 le) port)))))))
+               (receive (s ns) (floor/ (+ (* (date-second date) nano)
+                                          (date-nanosecond date))
+                                       nano)
+                 (display (number->string s) port)
+                 (display (locale-decimal-point) port)
+                 (let ((str (padding ns #\0 9)))
+                   (display (substring str 0 1) port)
+                   (display (string-trim-right str #\0 1) port)))))
    (cons #\h (lambda (date pad-with port)
                (display (date->string date "~b") port)))
    (cons #\H (lambda (date pad-with port)
diff --git a/test-suite/tests/srfi-19.test b/test-suite/tests/srfi-19.test
index 534cd7ca0..717047bb5 100644
--- a/test-suite/tests/srfi-19.test
+++ b/test-suite/tests/srfi-19.test
@@ -2,7 +2,7 @@
 ;;;; Matthias Koeppe <mkoeppe@mail.math.uni-magdeburg.de> --- June 2001
 ;;;;
 ;;;; Copyright (C) 2001, 2003, 2004, 2005, 2006, 2007, 2008,
-;;;;   2011, 2014 Free Software Foundation, Inc.
+;;;;   2011, 2014, 2017 Free Software Foundation, Inc.
 ;;;;
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -180,6 +180,10 @@ incomplete numerical tower implementation.)"
       (equal? "099999999"
               (date->string date "~N"))))
 
+  (pass-if "date->string correct ~f"
+    (let ((date (make-date 200000000 5 34 12 26 3 2017 0)))
+      (equal? "5.2" (date->string date "~f"))))
+
   ;; check time comparison procedures
   (let* ((time1 (make-time time-monotonic 0 0))
          (time2 (make-time time-monotonic 0 0))