diff --git a/core/math/integers/integers-tests.factor b/core/math/integers/integers-tests.factor
index c41ac78001..e83aeffb9e 100644
--- a/core/math/integers/integers-tests.factor
+++ b/core/math/integers/integers-tests.factor
@@ -272,3 +272,10 @@ IN: math.integers.tests
 { -1/0. } [ 2048 2^ -1 /f ] unit-test
 { -1/0. } [ 2048 2^ neg 1 /f ] unit-test
 { 1/0. } [ 2048 2^ neg -1 /f ] unit-test
+
+! bignum/f had a bug for results in ]0x1.0p-1022,0x0.4p-1022]
+! these are the first subnormals...
+{ 0x0.cp-1022 } [ 12 1026 2^ /f ] unit-test
+{ 0x0.8p-1022 } [ 8 1026 2^ /f ] unit-test
+{ 0x0.6p-1022 } [ 6 1026 2^ /f ] unit-test
+{ 0x0.4p-1022 } [ 4 1026 2^ /f ] unit-test
diff --git a/core/math/integers/integers.factor b/core/math/integers/integers.factor
index bee5cf6325..7d4f8ccb4a 100644
--- a/core/math/integers/integers.factor
+++ b/core/math/integers/integers.factor
@@ -142,7 +142,7 @@ M: bignum (log2) bignum-log2 ; inline
 : scale-float ( mantissa scale -- float' )
     {
         { [ dup 1024 > ] [ 2drop 1/0. ] }
-        { [ dup -1023 < ] [ 1021 + shift bits>double ] }
+        { [ dup -1021 < ] [ 1021 + shift bits>double ] }
         [ [ 52 2^ 1 - bitand ] dip 1022 + 52 shift bitor bits>double ]
     } cond ; inline