diff --git a/reasoning/nand/nand.n3 b/reasoning/nand/nand.n3
index 1213b4e03..5bdb0bf18 100644
--- a/reasoning/nand/nand.n3
+++ b/reasoning/nand/nand.n3
@@ -4,7 +4,6 @@
 
 @prefix list: <http://www.w3.org/2000/10/swap/list#>.
 @prefix graph: <http://www.w3.org/2000/10/swap/graph#>.
-@prefix math: <http://www.w3.org/2000/10/swap/math#>.
 @prefix log: <http://www.w3.org/2000/10/swap/log#>.
 
 # contrapositive rules