diff --git a/lib/srfi/166/test.sld b/lib/srfi/166/test.sld
index 47134ae5..a6a2f9c1 100644
--- a/lib/srfi/166/test.sld
+++ b/lib/srfi/166/test.sld
@@ -279,6 +279,9 @@
       (test "12.3µm" (show #f (numeric/si 1.23e-5 1000) "m")) ;?
       (test "1.2µm" (show #f (numeric/si 1.23e-6 1000) "m"))
       (test "1.2 µm" (show #f (numeric/si 1.23e-6 1000 " ") "m"))
+      (test "0" (show #f (numeric/si 0)))
+      (test "-608" (show #f (numeric/si -608)))
+      (test "-4k" (show #f (numeric/si -3986)))
 
       (test "1,234,567" (show #f (numeric/comma 1234567)))
       (test "1,234,567" (show #f (numeric/comma 1234567 3)))
diff --git a/lib/srfi/166/write.scm b/lib/srfi/166/write.scm
index 7c58eae3..0bdfb3d8 100644
--- a/lib/srfi/166/write.scm
+++ b/lib/srfi/166/write.scm
@@ -365,21 +365,25 @@
     (lambda (n . o)
       (let-optionals* o ((base 1000)
                          (separator ""))
-        (let* ((log-n (log n))
-               (names  (if (negative? log-n)
-                           (if (= base 1024) names-2 names-10)
-                           (if (= base 1024) names2 names10)))
-               (k (min (exact ((if (negative? log-n) ceiling floor)
-                               (/ (abs log-n) (log base))))
-                       (- (vector-length names) 1)))
-               (n2 (round-to (/ n (expt base (if (negative? log-n) (- k) k)))
-                             10)))
-          (each (if (integer? n2)
-                    (number->string (exact n2))
-                    (inexact n2))
-                ;; (if (zero? k) "" separator)
-                separator
-                (vector-ref names k)))))))
+        (if (zero? n)
+            "0"
+            (let* ((log-n (log (abs n)))
+                   (names  (if (negative? log-n)
+                               (if (= base 1024) names-2 names-10)
+                               (if (= base 1024) names2 names10)))
+                   (k (min (exact ((if (negative? log-n) ceiling floor)
+                                   (/ (abs log-n) (log base))))
+                           (- (vector-length names) 1)))
+                   (n2 (round-to (/ (abs n)
+                                    (expt base (if (negative? log-n) (- k) k)))
+                                 10)))
+              (each (if (negative? n) "-" "")
+                    (if (integer? n2)
+                        (number->string (exact n2))
+                        (inexact n2))
+                    ;; (if (zero? k) "" separator)
+                    separator
+                    (vector-ref names k))))))))
 
 ;; Force a number into a fixed width, print as #'s if doesn't fit.
 ;; Needs to be wrapped in PADDED if you want to expand to the width.