diff --git a/django/contrib/gis/gdal/srs.py b/django/contrib/gis/gdal/srs.py
index 2e335fe5d5..4df4419026 100644
--- a/django/contrib/gis/gdal/srs.py
+++ b/django/contrib/gis/gdal/srs.py
@@ -158,11 +158,15 @@ class SpatialReference(GDALBase):
 
     def auth_name(self, target):
         "Return the authority name for the given string target node."
-        return capi.get_auth_name(self.ptr, force_bytes(target))
+        return capi.get_auth_name(
+            self.ptr, target if target is None else force_bytes(target)
+        )
 
     def auth_code(self, target):
         "Return the authority code for the given string target node."
-        return capi.get_auth_code(self.ptr, force_bytes(target))
+        return capi.get_auth_code(
+            self.ptr, target if target is None else force_bytes(target)
+        )
 
     def clone(self):
         "Return a clone of this SpatialReference object."
diff --git a/tests/gis_tests/gdal_tests/test_srs.py b/tests/gis_tests/gdal_tests/test_srs.py
index fd25dcbc34..293144aa8e 100644
--- a/tests/gis_tests/gdal_tests/test_srs.py
+++ b/tests/gis_tests/gdal_tests/test_srs.py
@@ -35,7 +35,11 @@ srlist = (
         ang_name="degree",
         lin_units=1.0,
         ang_units=0.0174532925199,
-        auth={"GEOGCS": ("EPSG", "4326"), "spheroid": ("EPSG", "7030")},
+        auth={
+            None: ("EPSG", "4326"),  # Top-level authority.
+            "GEOGCS": ("EPSG", "4326"),
+            "spheroid": ("EPSG", "7030"),
+        },
         attr=(
             ("DATUM", "WGS_1984"),
             (("SPHEROID", 1), "6378137"),
@@ -64,6 +68,7 @@ srlist = (
         lin_units=1.0,
         ang_units=0.0174532925199,
         auth={
+            None: ("EPSG", "32140"),  # Top-level authority.
             "PROJCS": ("EPSG", "32140"),
             "spheroid": ("EPSG", "7019"),
             "unit": ("EPSG", "9001"),