diff --git a/contrib/math/utils.factor b/contrib/math/utils.factor
index a27fc402d3..27d791a704 100644
--- a/contrib/math/utils.factor
+++ b/contrib/math/utils.factor
@@ -31,3 +31,7 @@ USING: errors kernel sequences math ;
 : c. ( v v -- x )
     #! Complex inner product.
     0 [ ** + ] 2reduce ;
+
+: inv
+    #! inverse
+    1 swap / ; inline