diff --git a/xarray/tests/test_backends.py b/xarray/tests/test_backends.py
index bad9e99c042..1888f0767be 100644
--- a/xarray/tests/test_backends.py
+++ b/xarray/tests/test_backends.py
@@ -3356,3 +3356,14 @@ def test_no_warning_from_dask_effective_get():
             ds = Dataset()
             ds.to_netcdf(tmpfile)
         assert len(record) == 0
+
+
+@requires_scipy_or_netCDF4
+def test_source_encoding_always_present():
+    # Test for GH issue #2550.
+    rnddata = np.random.randn(10)
+    original = Dataset({'foo': ('x', rnddata)})
+    with create_tmp_file() as tmp:
+        original.to_netcdf(tmp)
+        with open_dataset(tmp) as ds:
+            assert ds.encoding['source'] == tmp