diff --git a/lib/wabanex_web/schema/types/custom/date_range.ex b/lib/wabanex_web/schema/types/custom/date_range.ex
index 45e2dd3..ebb1e40 100644
--- a/lib/wabanex_web/schema/types/custom/date_range.ex
+++ b/lib/wabanex_web/schema/types/custom/date_range.ex
@@ -17,10 +17,11 @@ defmodule WabanexWeb.Schema.Types.Custom.DateRange do
   end
 
   @spec serialize_range(PgRanges.DateRange.t()) :: String.t()
-  @spec serialize_range(list(DateTime.t() | nil)) :: String.t()
+  @spec serialize_range(list(DateTime.t() | nil | atom)) :: String.t()
   defp serialize_range(%PgRanges.DateRange{lower: start_range, upper: end_range}),
     do: serialize_range([start_range, end_range])
 
+  defp serialize_range([start_range, :unbound]), do: serialize_range([start_range, nil])
   defp serialize_range([start_range, nil]), do: "#{Date.to_iso8601(start_range)},"
 
   defp serialize_range([start_range, end_range]),
diff --git a/test/wabanex_web/schema/types/custom/date_range_test.exs b/test/wabanex_web/schema/types/custom/date_range_test.exs
index 2a1cb99..90077fb 100644
--- a/test/wabanex_web/schema/types/custom/date_range_test.exs
+++ b/test/wabanex_web/schema/types/custom/date_range_test.exs
@@ -28,6 +28,7 @@ defmodule WabanexWeb.Schema.Types.Custom.DateRangeTest do
     test "serialize a list of dates as a list of ISO8601 date strings" do
       assert "1978-12-15,1980-02-13" == serialize(:date_range, [~D[1978-12-15], ~D[1980-02-13]])
       assert "1978-12-15," == serialize(:date_range, [~D[1978-12-15], nil])
+      assert "1978-12-15," == serialize(:date_range, [~D[1978-12-15], :unbound])
     end
 
     test "serialize a postgres range as a list of ISO8601 date strings" do
@@ -35,6 +36,7 @@ defmodule WabanexWeb.Schema.Types.Custom.DateRangeTest do
                serialize(:date_range, DateRange.new(~D[1978-12-15], ~D[1980-02-13]))
 
       assert "1978-12-15," == serialize(:date_range, DateRange.new(~D[1978-12-15], nil))
+      assert "1978-12-15," == serialize(:date_range, DateRange.new(~D[1978-12-15], :unbound))
     end
 
     test "can be parsed from a string of ISO8601" do