diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 3e17a29..7f423c1 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -1295,6 +1295,11 @@
         self.addCleanup(os.close, fds[1])
 
         open_fds = set(fds)
+        # add a bunch more fds
+        for _ in range(9):
+            fd = os.open("/dev/null", os.O_RDONLY)
+            self.addCleanup(os.close, fd)
+            open_fds.add(fd)
 
         p = subprocess.Popen([sys.executable, fd_status],
                              stdout=subprocess.PIPE, close_fds=False)
@@ -1313,6 +1318,19 @@
                          "Some fds were left open")
         self.assertIn(1, remaining_fds, "Subprocess failed")
 
+        # Keep some of the fd's we opened open in the subprocess.
+        # This tests _posixsubprocess.c's proper handling of fds_to_keep.
+        fds_to_keep = set(open_fds.pop() for _ in range(8))
+        p = subprocess.Popen([sys.executable, fd_status],
+                             stdout=subprocess.PIPE, close_fds=True,
+                             pass_fds=())
+        output, ignored = p.communicate()
+        remaining_fds = set(map(int, output.split(b',')))
+
+        self.assertFalse(remaining_fds & fds_to_keep & open_fds,
+                         "Some fds not in pass_fds were left open")
+        self.assertIn(1, remaining_fds, "Subprocess failed")
+
     # Mac OS X Tiger (10.4) has a kernel bug: sometimes, the file
     # descriptor of a pipe closed in the parent process is valid in the
     # child process according to fstat(), but the mode of the file