diff --git a/extra/math/derivatives/derivatives.factor b/extra/math/derivatives/derivatives.factor
index fef93cabc4..d92066efaf 100644
--- a/extra/math/derivatives/derivatives.factor
+++ b/extra/math/derivatives/derivatives.factor
@@ -3,7 +3,8 @@
 USING: kernel math math.points math.function-tools ;
 IN: math.derivatives
 
-: small-amount ( -- n ) 1.0e-12 ;
-: near ( x -- y ) small-amount + ;
-: derivative ( x function -- m ) 2dup [ near ] dip [ eval ] 2bi@ slope ;
+: small-amount ( -- n ) 1.0e-14 ;
+: some-more ( x -- y ) small-amount + ;
+: some-less ( x -- y ) small-amount - ;
+: derivative ( x function -- m ) [ [ some-more ] dip eval ] [ [ some-less ] dip eval ] 2bi slope ;
 : derivative-func ( function -- function ) [ derivative ] curry ;
\ No newline at end of file