diff --git a/core/math/floats/floats-tests.factor b/core/math/floats/floats-tests.factor
index ae72aba67f..d8d4e03b0f 100644
--- a/core/math/floats/floats-tests.factor
+++ b/core/math/floats/floats-tests.factor
@@ -93,3 +93,12 @@ unit-test
 
 [ 5.0 ] [ 3 5.0 max ] unit-test
 [ 3 ] [ 3 5.0 min ] unit-test
+
+{ 39 0x1.999999999998ap-4 } [ 4.0 .1 /mod ] unit-test
+{ 38 0x1.9999999999984p-4 } [ 3.9 .1 /mod ] unit-test
+{ 39 0x1.999999999998ap-4 } [ 4.0 -.1 /mod ] unit-test
+{ 38 0x1.9999999999984p-4 } [ 3.9 -.1 /mod ] unit-test
+{ 39 -0x1.999999999998ap-4 } [ -4.0 -.1 /mod ] unit-test
+{ 38 -0x1.9999999999984p-4 } [ -3.9 -.1 /mod ] unit-test
+{ 39 -0x1.999999999998ap-4 } [ -4.0 .1 /mod ] unit-test
+{ 38 -0x1.9999999999984p-4 } [ -3.9 .1 /mod ] unit-test
diff --git a/core/math/floats/floats.factor b/core/math/floats/floats.factor
index 3fa9be4cad..58f40d2ffc 100644
--- a/core/math/floats/floats.factor
+++ b/core/math/floats/floats.factor
@@ -38,7 +38,7 @@ M: float /i float/f >integer ; inline
 
 M: real abs dup 0 < [ neg ] when ; inline
 
-M: real /mod [ /i ] [ mod ] 2bi ; inline
+M: real /mod dupd mod [ [ - ] [ /i ] bi ] keep ; inline
 
 M: float fp-special?
     double>bits -52 shift 0x7ff [ bitand ] keep = ; inline