diff --git a/src/encoded/tests/test_schema_library.py b/src/encoded/tests/test_schema_library.py
index 295d772a067..9dac01bc761 100644
--- a/src/encoded/tests/test_schema_library.py
+++ b/src/encoded/tests/test_schema_library.py
@@ -144,7 +144,7 @@ def test_library_biosample_and_mixed_biosample(testapp, library, biosample_1, bi
     testapp.post_json('/library', library, status=201)
     library.update({'mixed_biosamples': [biosample_1['@id'], biosample_2['@id']]})
     testapp.post_json('/library', library, status=201)
-    library.update({'biosample': biosample_2})
+    library.update({'biosample': biosample_2['@id']})
     testapp.post_json('/library', library, status=422)