diff --git a/altair/vegalite/v3/api.py b/altair/vegalite/v3/api.py
index 2b372f357..ceef45ef9 100644
--- a/altair/vegalite/v3/api.py
+++ b/altair/vegalite/v3/api.py
@@ -1882,8 +1882,7 @@ def add_selection(self, *selections):
         if not selections or not self.layer:
             return self
         copy = self.copy()
-        copy.layer = [chart.add_selection(*selections)
-                        for chart in copy.layer]
+        copy.layer[0] = copy.layer[0].add_selection(*selections)
         return copy
 
 
diff --git a/altair/vegalite/v3/tests/test_api.py b/altair/vegalite/v3/tests/test_api.py
index caaa9fc81..8400b3c6e 100644
--- a/altair/vegalite/v3/tests/test_api.py
+++ b/altair/vegalite/v3/tests/test_api.py
@@ -535,7 +535,15 @@ def test_facet_add_selections():
     assert chart1.to_dict() == chart2.to_dict()
 
 
-@pytest.mark.parametrize('charttype', [alt.layer, alt.concat, alt.hconcat, alt.vconcat])
+def test_layer_add_selection():
+    base = alt.Chart('data.csv').mark_point()
+    selection = alt.selection_single()
+    chart1 = alt.layer(base.add_selection(selection), base)
+    chart2 = alt.layer(base, base).add_selection(selection)
+    assert chart1.to_dict() == chart2.to_dict()
+
+
+@pytest.mark.parametrize('charttype', [alt.concat, alt.hconcat, alt.vconcat])
 def test_compound_add_selections(charttype):
     base = alt.Chart('data.csv').mark_point()
     selection = alt.selection_single()