diff --git a/core/math/integers/integers-tests.factor b/core/math/integers/integers-tests.factor
index 76ce162d7d..44c038b6ee 100644
--- a/core/math/integers/integers-tests.factor
+++ b/core/math/integers/integers-tests.factor
@@ -229,3 +229,4 @@ unit-test
 
 ! Ensure that /f is accurate for fixnums > 2^53 on 64-bit platforms
 [ HEX: 1.758bec11492f9p-54 ] [ 1 12345678901234567 /f ] unit-test
+[ HEX: -1.758bec11492f9p-54 ] [ 1 -12345678901234567 /f ] unit-test
diff --git a/core/math/integers/integers.factor b/core/math/integers/integers.factor
index da8b8b9edc..eb94597160 100644
--- a/core/math/integers/integers.factor
+++ b/core/math/integers/integers.factor
@@ -41,7 +41,7 @@ CONSTANT: bignum/f-threshold HEX: 20,0000,0000,0000
     [ >float ] bi@ float/f ; inline
 
 M: fixnum /f
-    2dup [ bignum/f-threshold >= ] either?
+    2dup [ abs bignum/f-threshold >= ] either?
     [ bignum/f ] [ fixnum/f ] if ; inline
 
 M: fixnum mod fixnum-mod ; inline