diff -r 6e66319e7ad8 Modules/socketmodule.c
--- a/Modules/socketmodule.c	Wed Sep 14 23:53:47 2016 -0700
+++ b/Modules/socketmodule.c	Fri Sep 16 10:36:14 2016 +0200
@@ -4683,6 +4683,10 @@
         else
 #endif
         {
+            struct sockaddr sa;
+            socklen_t slen;
+            int tmp;
+
             fd = PyLong_AsSocket_t(fdobj);
             if (fd == (SOCKET_T)(-1) && PyErr_Occurred())
                 return -1;
@@ -4691,6 +4695,25 @@
                                 "can't use invalid socket value");
                 return -1;
             }
+            /* Get family, type and proto from fd. Ignores all errors and
+             * keeps the arguments that have been passed in by the user.
+             */
+            slen = sizeof(sa);
+            if (getsockname(fd, &sa, &slen) == 0) {
+                family = sa.sa_family;
+            }
+#ifdef SO_TYPE
+            slen = sizeof(tmp);
+            if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &tmp, &slen) == 0) {
+                type = tmp;
+            }
+#endif
+#ifdef SO_PROTOCOL
+            slen = sizeof(tmp);
+            if (getsockopt(fd, SOL_SOCKET, SO_PROTOCOL, &tmp, &slen) == 0) {
+                proto = tmp;
+            }
+#endif
         }
     }
     else {