diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index d6e94f0c5..bd9e71ffa 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,19 @@
+2015-03-18  Corinna Vinschen  <corinna@vinschen.de>
+
+	* grp.cc (pwdgrp::parse_group): Call cygsid::getfromgr_passwd.
+	* passwd.cc (pwdgrp::parse_passwd): Call cygsid::getfrompw_gecos.
+	* pwdgrp.h (cygsid::getfrompw): Implement as inline method here,
+	accessing pg_pwd's sid member directly.
+	(cygsid::getfromgr): Implement as inline method here, accessing
+	pg_grp's sid member directly.
+	* sec_auth.cc (extract_nt_dom_user): Call cygsid::getfrompw_gecos.
+	Explain why.
+	* sec_helper.cc (cygsid::getfrompw): Drop implementation.
+	(cygsid::getfromgr): Ditto.
+	* security.h (cygsid::getfrompw_gecos): Implement former getfrompw
+	inline here.
+	(cygsid::getfromgr_passwd): Implement former getfromgr inline here.
+
 2015-03-18  Corinna Vinschen  <corinna@vinschen.de>
 
 	* sec_auth.cc (get_server_groups): Drop unused passwd argument.  Adjust
diff --git a/winsup/cygwin/grp.cc b/winsup/cygwin/grp.cc
index 53551161a..ea20e926c 100644
--- a/winsup/cygwin/grp.cc
+++ b/winsup/cygwin/grp.cc
@@ -47,7 +47,7 @@ pwdgrp::parse_group ()
     return false;
   /* Don't generate gr_mem entries. */
   grp.g.gr_mem = &null_ptr;
-  grp.sid.getfromgr (&grp.g);
+  grp.sid.getfromgr_passwd (&grp.g);
   return true;
 }
 
diff --git a/winsup/cygwin/passwd.cc b/winsup/cygwin/passwd.cc
index 825b2e0a8..7493aa443 100644
--- a/winsup/cygwin/passwd.cc
+++ b/winsup/cygwin/passwd.cc
@@ -40,7 +40,7 @@ pwdgrp::parse_passwd ()
   res.p.pw_gecos = next_str (':');
   res.p.pw_dir =  next_str (':');
   res.p.pw_shell = next_str (':');
-  res.sid.getfrompw (&res.p);
+  res.sid.getfrompw_gecos (&res.p);
   /* lptr points to the \0 after pw_shell.  Increment by one to get the correct
      required buffer len in getpw_cp. */
   res.len = lptr - res.p.pw_name + 1;
diff --git a/winsup/cygwin/pwdgrp.h b/winsup/cygwin/pwdgrp.h
index 8a78d305f..dc718c596 100644
--- a/winsup/cygwin/pwdgrp.h
+++ b/winsup/cygwin/pwdgrp.h
@@ -246,3 +246,11 @@ public:
   struct group *getgrent ();
   inline void endgrent () { endent (true); }
 };
+
+/* These inline methods have to be defined here so that pg_pwd and pg_grp
+   are defined. */
+inline BOOL cygsid::getfrompw (const struct passwd *pw)
+  { return (*this = pw ? (PSID) ((pg_pwd *) pw)->sid : NO_SID) != NO_SID; }
+
+inline BOOL cygsid::getfromgr (const struct group *gr)
+  { return (*this = gr ? (PSID) ((pg_grp *) gr)->sid : NO_SID) != NO_SID; }
diff --git a/winsup/cygwin/sec_auth.cc b/winsup/cygwin/sec_auth.cc
index aeb571de6..d5fa76def 100644
--- a/winsup/cygwin/sec_auth.cc
+++ b/winsup/cygwin/sec_auth.cc
@@ -119,7 +119,10 @@ extract_nt_dom_user (const struct passwd *pw, PWCHAR domain, PWCHAR user)
 
   debug_printf ("pw_gecos %p (%s)", pw->pw_gecos, pw->pw_gecos);
 
-  if (psid.getfrompw (pw)
+  /* The incoming passwd entry is not necessarily a pointer to the
+     internal passwd buffers, thus we must not rely on being able to
+     cast it to pg_pwd. */
+  if (psid.getfrompw_gecos (pw)
       && LookupAccountSidW (NULL, psid, user, &ulen, domain, &dlen, &use))
     return;
 
diff --git a/winsup/cygwin/sec_helper.cc b/winsup/cygwin/sec_helper.cc
index 946e78a8e..679f3a858 100644
--- a/winsup/cygwin/sec_helper.cc
+++ b/winsup/cygwin/sec_helper.cc
@@ -1,7 +1,7 @@
 /* sec_helper.cc: NT security helper functions
 
    Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
-   2011, 2012, 2013, 2014 Red Hat, Inc.
+   2011, 2012, 2013, 2014, 2015 Red Hat, Inc.
 
    Written by Corinna Vinschen <corinna@vinschen.de>
 
@@ -279,20 +279,6 @@ cygsid::getfromstr (const char *nsidstr, bool well_known)
   return psid = NO_SID;
 }
 
-BOOL
-cygsid::getfrompw (const struct passwd *pw)
-{
-  char *sp = (pw && pw->pw_gecos) ? strrchr (pw->pw_gecos, ',') : NULL;
-  return (*this = sp ? sp + 1 : sp) != NULL;
-}
-
-BOOL
-cygsid::getfromgr (const struct group *gr)
-{
-  char *sp = (gr && gr->gr_passwd) ? gr->gr_passwd : NULL;
-  return (*this = sp) != NULL;
-}
-
 cygsid *
 cygsidlist::alloc_sids (int n)
 {
diff --git a/winsup/cygwin/security.h b/winsup/cygwin/security.h
index 6af87e0d4..867345774 100644
--- a/winsup/cygwin/security.h
+++ b/winsup/cygwin/security.h
@@ -237,6 +237,18 @@ public:
 
   inline PSID set () { return psid = (PSID) sbuf; }
 
+  inline BOOL getfrompw_gecos (const struct passwd *pw)
+    {
+      char *sp = (pw && pw->pw_gecos) ? strrchr (pw->pw_gecos, ',') : NULL;
+      return (*this = sp ? sp + 1 : sp) != NO_SID;
+    }
+  inline BOOL getfromgr_passwd (const struct group *gr)
+    {
+      char *sp = (gr && gr->gr_passwd) ? gr->gr_passwd : NULL;
+      return (*this = sp) != NO_SID;
+    }
+
+  /* Implemented in pwdgrp.h. */
   BOOL getfrompw (const struct passwd *pw);
   BOOL getfromgr (const struct group *gr);