diff --git a/kwant/tests/test_builder.py b/kwant/tests/test_builder.py
index 7ba00b403513ffe3100acd184820adf1c788ed15..e0ed4bfe274998b684f89d167386f1911ff9c270 100644
--- a/kwant/tests/test_builder.py
+++ b/kwant/tests/test_builder.py
@@ -1275,7 +1275,7 @@ def test_argument_passing():
 
     # Some common, some different args for value functions
     def onsite2(site, a, b):
-        return site.pos + a + b
+        return site.pos[0] + a + b
 
     def hopping2(site1, site2, a, c, b):
         return a + b + c
diff --git a/kwant/tests/test_operator.py b/kwant/tests/test_operator.py
index bb8a185e6675356d90552ee3d21b06d241fda83c..c5111b75d88033a74654eb5aa8e0661ee2dc51e9 100644
--- a/kwant/tests/test_operator.py
+++ b/kwant/tests/test_operator.py
@@ -445,7 +445,7 @@ def test_arg_passing(A):
     lat1 = kwant.lattice.chain(norbs=1)
 
     syst = kwant.Builder()
-    syst[lat1(0)] = syst[lat1(1)] = lambda s0, a, b: s0.pos + a + b
+    syst[lat1(0)] = syst[lat1(1)] = lambda s0, a, b: s0.pos[0] + a + b
     syst[lat1.neighbors()] = lambda s0, s1, a, b: a - b
     fsyst = syst.finalized()