diff --git a/src/_pytest/fixtures.py b/src/_pytest/fixtures.py
index <HASH>..<HASH> 100644
--- a/src/_pytest/fixtures.py
+++ b/src/_pytest/fixtures.py
@@ -93,7 +93,7 @@ def get_scope_package(node, fixturedef):
 
     cls = pytest.Package
     current = node
-    fixture_package_name = os.path.join(fixturedef.baseid, "__init__.py")
+    fixture_package_name = "%s/%s" % (fixturedef.baseid, "__init__.py")
     while current and (
         type(current) is not cls or fixture_package_name != current.nodeid
     ):
Fix the package fixture ordering in Windows.