diff --git a/extra/units/units-tests.factor b/extra/units/units-tests.factor
index 72c3b108ea..28ab9ab7c4 100644
--- a/extra/units/units-tests.factor
+++ b/extra/units/units-tests.factor
@@ -1,5 +1,5 @@
 USING: arrays kernel math sequences tools.test units.si
-units.imperial units inverse ;
+units.imperial units inverse math.functions ;
 IN: temporary
 
 [ T{ dimensioned f 3 { m } { } } ] [ 3 m ] unit-test