diff --git a/module/rnrs/arithmetic/fixnums.scm b/module/rnrs/arithmetic/fixnums.scm
index e6261999a..dbf9ee746 100644
--- a/module/rnrs/arithmetic/fixnums.scm
+++ b/module/rnrs/arithmetic/fixnums.scm
@@ -1,6 +1,6 @@
 ;;; fixnums.scm --- The R6RS fixnums arithmetic library
 
-;;      Copyright (C) 2010, 2011 Free Software Foundation, Inc.
+;;      Copyright (C) 2010, 2011, 2013 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
@@ -227,7 +227,12 @@
     (assert-fixnum fx1 fx2 fx3) 
     (bitwise-if fx1 fx2 fx3))
 
-  (define (fxbit-count fx) (assert-fixnum fx) (logcount fx))
+  (define (fxbit-count fx)
+    (assert-fixnum fx)
+    (if (negative? fx)
+        (bitwise-not (logcount fx))
+        (logcount fx)))
+
   (define (fxlength fx) (assert-fixnum fx) (bitwise-length fx))
   (define (fxfirst-bit-set fx) (assert-fixnum fx) (bitwise-first-bit-set fx))
   (define (fxbit-set? fx1 fx2) (assert-fixnum fx1 fx2) (logbit? fx2 fx1))
diff --git a/test-suite/tests/r6rs-arithmetic-fixnums.test b/test-suite/tests/r6rs-arithmetic-fixnums.test
index d39d5448b..01a7a89b2 100644
--- a/test-suite/tests/r6rs-arithmetic-fixnums.test
+++ b/test-suite/tests/r6rs-arithmetic-fixnums.test
@@ -1,6 +1,6 @@
 ;;; arithmetic-fixnums.test --- Test suite for R6RS (rnrs arithmetic bitwise)
 
-;;      Copyright (C) 2010, 2011 Free Software Foundation, Inc.
+;;      Copyright (C) 2010, 2011, 2013 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
@@ -157,7 +157,9 @@
 
 (with-test-prefix "fxif" (pass-if "simple" (fx=? (fxif 5 3 4) 1)))
 
-(with-test-prefix "fxbit-count" (pass-if "simple" (fx=? (fxbit-count 5) 2)))
+(with-test-prefix "fxbit-count"
+  (pass-if "simple" (fx=? (fxbit-count 5) 2))
+  (pass-if "negative" (fx=? (fxbit-count -5) -2)))
 
 (with-test-prefix "fxlength" (pass-if "simple" (fx=? (fxlength 5) 3)))