diff --git a/tests/fields/test_edge_data_field.py b/tests/fields/test_edge_data_field.py
index 6863203..090fe20 100644
--- a/tests/fields/test_edge_data_field.py
+++ b/tests/fields/test_edge_data_field.py
@@ -12,7 +12,7 @@ def field():
 @pytest.mark.parametrize('text,value,exc', [
     ('1 2\n2 3\n-1', [(1, 2), (2, 3)], None),
     ('1 2\n2 x\n-1', [(1, 2), (2, 3)], E.ParsingError),
-    ('1 2 3\n2 3\n-1', {1: [2, 3], 2: [3]}, None),
+    ('1 2 3 -1\n2 3 -1\n-1', {1: [2, 3], 2: [3]}, None),
     ('1 x 3\n2 3\n-1', {1: [2, 3], 2: [3]}, E.ParsingError),
 ])
 def test_parse(field, text, value, exc):
@@ -20,4 +20,4 @@ def test_parse(field, text, value, exc):
         with pytest.raises(exc):
             field.parse(text)
     else:
-        field.parse(text) == value
+        assert field.parse(text) == value
diff --git a/tests/fields/test_edge_list_field.py b/tests/fields/test_edge_list_field.py
index 215ce8a..cbd823a 100644
--- a/tests/fields/test_edge_list_field.py
+++ b/tests/fields/test_edge_list_field.py
@@ -9,7 +9,7 @@ def edge_list_field():
 
 
 def test_parse(edge_list_field):
-    assert edge_list_field.parse('1 2\n3 4\n-1') == [[1, 2], [3, 4]]
+    assert edge_list_field.parse('1 2\n3 4\n-1') == [(1, 2), (3, 4)]
 
 
 def test_render(edge_list_field):
diff --git a/tsplib95/fields.py b/tsplib95/fields.py
index 7de9b88..6f3e084 100644
--- a/tsplib95/fields.py
+++ b/tsplib95/fields.py
@@ -237,8 +237,8 @@ class AdjacencyListField(TransformerField):
     @classmethod
     def build_transformer(cls):
         return T.MapT(key=T.FuncT(func=int),
-                      value=T.ListT(value=T.FuncT(func=int)),
-                      sep=('-1', ' -1\n'),
+                      value=T.ListT(value=T.FuncT(func=int), terminal='-1'),
+                      sep='\n',
                       terminal='-1')
 
 
@@ -249,7 +249,7 @@ class EdgeListField(TransformerField):
 
     @classmethod
     def build_transformer(cls):
-        edge = T.ListT(value=T.FuncT(func=int), size=2)
+        edge = T.TupleT(value=T.FuncT(func=int), size=2)
         return T.ListT(value=edge, terminal='-1', sep='\n')
 
 
@@ -273,7 +273,7 @@ class EdgeDataField(TransformerField):
     def build_transformer(cls):
         adj_list = AdjacencyListField.build_transformer()
         edge_list = EdgeListField.build_transformer()
-        return T.UnionT(adj_list, edge_list)
+        return T.UnionT(edge_list, adj_list)
 
 
 class DepotsField(TransformerField):
diff --git a/tsplib95/transformers.py b/tsplib95/transformers.py
index 7536349..a2dc33d 100644
--- a/tsplib95/transformers.py
+++ b/tsplib95/transformers.py
@@ -244,6 +244,14 @@ def pack(self, items):
     def unpack(self, container):
         return list(container)
 
+class TupleT(ContainerT):
+    """Transformer for tuples"""
+
+    def pack(self, items):
+        return tuple(items)
+
+    def unpack(self, container):
+        return tuple(container)
 
 class MapT(ContainerT):
     """Transformer for a key-value mapping of items.