diff --git a/moldesign/_tests/test_biopython_xface.py b/moldesign/_tests/test_biopython_xface.py
index 94794fa..3812a83 100644
--- a/moldesign/_tests/test_biopython_xface.py
+++ b/moldesign/_tests/test_biopython_xface.py
@@ -1,4 +1,4 @@
-
+import io
 import pytest
 import Bio.PDB
 import moldesign as mdt
@@ -9,8 +9,10 @@
 
 @pytest.fixture
 def biopy_3aid():
+    import gzip
     parser = Bio.PDB.PDBParser()
-    structure = parser.get_structure('3aid', get_data_path('3aid.pdb.gz'))
+    s = gzip.open(get_data_path('3aid.pdb.gz'), 'r').read().decode('utf-8')
+    structure = parser.get_structure('3aid', io.StringIO(s))
     return structure