diff --git a/planet/cli/subscriptions.py b/planet/cli/subscriptions.py
index 4cc65c3d..05568b86 100644
--- a/planet/cli/subscriptions.py
+++ b/planet/cli/subscriptions.py
@@ -514,10 +514,10 @@ def request_pv(var_type, var_id, geometry, start_time, end_time, pretty):
     more details.
     """
     res = subscription_request.planetary_variable_source(
-        var_type,
         var_id,
         geometry,
         start_time,
+        var_type=var_type,
         end_time=end_time,
     )
     echo_json(res, pretty)
diff --git a/planet/subscription_request.py b/planet/subscription_request.py
index 8fb52a00..79f68304 100644
--- a/planet/subscription_request.py
+++ b/planet/subscription_request.py
@@ -285,10 +285,10 @@ def catalog_source(
 
 
 def planetary_variable_source(
-    var_type: Optional[str],
     var_id: str,
     geometry: Union[dict, str],
     start_time: datetime,
+    var_type: Optional[str] = None,
     end_time: Optional[datetime] = None,
 ) -> dict:
     """Construct a Planetary Variable subscription source.
@@ -304,9 +304,6 @@ def planetary_variable_source(
     Note: this function does not validate variable types and ids.
 
     Parameters:
-        var_type: Planetary Variable type. See documentation for all
-            available types.  Used to be a required parameter but
-            is now optional and can be 'None'.
         var_id: A Planetary Variable ID. See documenation for all
             available IDs.
         geometry: The area of interest of the subscription that will be
@@ -314,6 +311,9 @@ def planetary_variable_source(
             Features API geometry reference (string)
         start_time: The start time of the subscription. This time can be
             in the past or future.
+        var_type: Planetary Variable type. See documentation for all
+            available types.  Used to be a required parameter but
+            is now optional and can be 'None'.
         end_time: The end time of the subscription. This time can be in
             the past or future, and must be after the start_time.
 
diff --git a/tests/unit/test_subscription_request.py b/tests/unit/test_subscription_request.py
index deafbf94..0995527a 100644
--- a/tests/unit/test_subscription_request.py
+++ b/tests/unit/test_subscription_request.py
@@ -576,10 +576,10 @@ def test_toar_tool_success():
 def test_pv_source_success(geom_geojson, var_type, var_id):
     """Configure a planetary variable subscription source."""
     source = subscription_request.planetary_variable_source(
-        var_type,
         var_id,
         geometry=geom_geojson,
         start_time=datetime(2021, 3, 1),
+        var_type=var_type,
         end_time=datetime(2021, 3, 2),
     )
 
@@ -593,6 +593,17 @@ def test_pv_source_success(geom_geojson, var_type, var_id):
     assert params["start_time"].startswith("2021-03-01")
 
 
+def test_pv_source_no_type(geom_geojson):
+    """Configure a planetary variable subscription source."""
+    source = subscription_request.planetary_variable_source(
+        "BIOMASS-PROXY_V3.0_10",
+        geometry=geom_geojson,
+        start_time=datetime(2021, 3, 1),
+        end_time=datetime(2021, 3, 2),
+    )
+    assert source.get("type") is None
+
+
 @respx.mock
 @pytest.mark.parametrize(
     # Test all the combinations of the three options plus some with dupes.