diff --git a/nalaf/preprocessing/edges.py b/nalaf/preprocessing/edges.py
index 3953c3c0..f6627443 100644
--- a/nalaf/preprocessing/edges.py
+++ b/nalaf/preprocessing/edges.py
@@ -1,6 +1,5 @@
 import abc
 from nalaf.structures.data import Edge
-from nltk.stem import PorterStemmer
 
 class EdgeGenerator:
     """