diff --git a/kwant/lattice.py b/kwant/lattice.py
index 13e93a78cc0f27976c1cee7ce046f79ff0d91342..5b55b98890f984aad57944bfc3b1b8bf3d5b580a 100644
--- a/kwant/lattice.py
+++ b/kwant/lattice.py
@@ -394,7 +394,7 @@ class Monatomic(builder.SiteFamily, Polyatomic):
 
     Parameters
     ----------
-    prim_vecss : 2d array-like of floats
+    prim_vecs : 2d array-like of floats
         Primitive vectors of the Bravais lattice.
 
     offset : vector of floats