Index: subprocess.py
===================================================================
--- subprocess.py	(revision 53295)
+++ subprocess.py	(working copy)
@@ -717,6 +717,8 @@
 
         def _make_inheritable(self, handle):
             """Return a duplicate of handle, which is inheritable"""
+            if not handle:
+                return None
             return DuplicateHandle(GetCurrentProcess(), handle,
                                    GetCurrentProcess(), 0, 1,
                                    DUPLICATE_SAME_ACCESS)
@@ -752,12 +754,19 @@
             # Process startup details
             if startupinfo is None:
                 startupinfo = STARTUPINFO()
-            if None not in (p2cread, c2pwrite, errwrite):
-                startupinfo.dwFlags |= STARTF_USESTDHANDLES
-                startupinfo.hStdInput = p2cread
-                startupinfo.hStdOutput = c2pwrite
-                startupinfo.hStdError = errwrite
 
+            handles = []
+            for handle in (p2cread, c2pwrite, errwrite):
+                if handle is None:
+                    handle = -1  # INVALID_HANDLE_VALUE
+                else:
+                    startupinfo.dwFlags |= STARTF_USESTDHANDLES
+                handles.append(handle)
+
+            (startupinfo.hStdInput, 
+             startupinfo.hStdOutput, 
+             startupinfo.hStdError) = handles
+
             if shell:
                 startupinfo.dwFlags |= STARTF_USESHOWWINDOW
                 startupinfo.wShowWindow = SW_HIDE