diff --git a/libstdc++-v3/config/os/bsd/dragonfly/os_defines.h b/libstdc++-v3/config/os/bsd/dragonfly/os_defines.h
index c42c6e661630..0c63a0ee1fdd 100644
--- a/libstdc++-v3/config/os/bsd/dragonfly/os_defines.h
+++ b/libstdc++-v3/config/os/bsd/dragonfly/os_defines.h
@@ -38,4 +38,8 @@
 #define _GLIBCXX_USE_C99_LONG_LONG_CHECK 1
 #define _GLIBCXX_USE_C99_LONG_LONG_DYNAMIC (_GLIBCXX_USE_C99_DYNAMIC || !defined __LONG_LONG_SUPPORTED)
 
+// Make std::call_once access pthread_once_t members directly
+#define _GLIBCXX_COMPAT_PTHREAD_ONCE_T \
+  { int _M_done; pthread_mutex_t _M_mutex; }
+
 #endif
diff --git a/libstdc++-v3/config/os/bsd/freebsd/os_defines.h b/libstdc++-v3/config/os/bsd/freebsd/os_defines.h
index d896de4254f4..fbae94c0370d 100644
--- a/libstdc++-v3/config/os/bsd/freebsd/os_defines.h
+++ b/libstdc++-v3/config/os/bsd/freebsd/os_defines.h
@@ -40,4 +40,8 @@
 #define _GLIBCXX_USE_C99_FLOAT_TRANSCENDENTALS_CHECK 1
 #define _GLIBCXX_USE_C99_FLOAT_TRANSCENDENTALS_DYNAMIC defined _XOPEN_SOURCE
 
+// Make std::call_once access pthread_once_t members directly
+#define _GLIBCXX_COMPAT_PTHREAD_ONCE_T \
+  { int _M_done; pthread_mutex_t _M_mutex; }
+
 #endif
diff --git a/libstdc++-v3/config/os/bsd/netbsd/os_defines.h b/libstdc++-v3/config/os/bsd/netbsd/os_defines.h
index d15727e76e0a..0ab2e6528228 100644
--- a/libstdc++-v3/config/os/bsd/netbsd/os_defines.h
+++ b/libstdc++-v3/config/os/bsd/netbsd/os_defines.h
@@ -30,4 +30,8 @@
 
 #define __ssize_t ssize_t
 
+// Make std::call_once access pthread_once_t members directly
+#define _GLIBCXX_COMPAT_PTHREAD_ONCE_T \
+  { pthread_mutex_t _M_mutex; int _M_done; }
+
 #endif
diff --git a/libstdc++-v3/config/os/bsd/openbsd/os_defines.h b/libstdc++-v3/config/os/bsd/openbsd/os_defines.h
index 1761a10e3836..d248bd2cab29 100644
--- a/libstdc++-v3/config/os/bsd/openbsd/os_defines.h
+++ b/libstdc++-v3/config/os/bsd/openbsd/os_defines.h
@@ -38,4 +38,8 @@
 #define _GLIBCXX_USE_C99_FLOAT_TRANSCENDENTALS_DYNAMIC _GLIBCXX_USE_C99_DYNAMIC
 #define _GLIBCXX_USE_C99_FP_MACROS_DYNAMIC _GLIBCXX_USE_C99_DYNAMIC
 
+// Make std::call_once access pthread_once_t members directly
+#define _GLIBCXX_COMPAT_PTHREAD_ONCE_T \
+  { int _M_done; pthread_mutex_t _M_mutex; }
+
 #endif
diff --git a/libstdc++-v3/config/os/solaris/os_defines.h b/libstdc++-v3/config/os/solaris/os_defines.h
index 36e8cb786cbc..58b7a9f309d4 100644
--- a/libstdc++-v3/config/os/solaris/os_defines.h
+++ b/libstdc++-v3/config/os/solaris/os_defines.h
@@ -35,5 +35,9 @@
 #define __CORRECT_ISO_CPP_WCHAR_H_PROTO
 #endif
 
+// Make std::call_once access pthread_once_t members directly
+#define _GLIBCXX_COMPAT_PTHREAD_ONCE_T \
+  { pthread_mutex_t _M_mutex; unsigned _M_unused; unsigned _M_done; }
+
 #endif
 
diff --git a/libstdc++-v3/include/std/mutex b/libstdc++-v3/include/std/mutex
index 8c7664bff550..6d87834b3bfd 100644
--- a/libstdc++-v3/include/std/mutex
+++ b/libstdc++-v3/include/std/mutex
@@ -684,6 +684,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     enum _Bits : int { _Init = 0, _Active = 1, _Done = 2 };
 
     int _M_once = _Bits::_Init;
+#elif defined _GLIBCXX_COMPAT_PTHREAD_ONCE_T
+    struct _Once _GLIBCXX_COMPAT_PTHREAD_ONCE_T;
+    static_assert(sizeof(_Once) == sizeof(__gthread_once_t), "config error");
+    static_assert(alignof(_Once) == alignof(__gthread_once_t), "config error");
+    union
+    {
+      __gthread_once_t _M_native = __GTHREAD_ONCE_INIT;
+      _Once _M_once;
+    };
+#else
+    __gthread_once_t _M_once = __GTHREAD_ONCE_INIT;
+#endif // ! GTHREADS
 
     // Non-blocking query whether this is known to be a passive execution.
     bool
@@ -706,11 +718,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       once_flag& _M_flag;
       bool _M_returning = false;
     };
-#else
-    __gthread_once_t _M_once = __GTHREAD_ONCE_INIT;
 
     struct _Prepare_execution;
-#endif // ! GTHREADS
 
     template<typename _Callable, typename... _Args>
       friend void
@@ -753,7 +762,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   once_flag::_M_exceptional() noexcept
   { _M_once = _Bits::_Init; }
 
-#else // ! FUTEX && GTHREADS
+#elif defined _GLIBCXX_COMPAT_PTHREAD_ONCE_T
+
+  inline bool
+  once_flag::_M_passive() const noexcept
+  { return false; }
+
+#else
 
   /// @cond undocumented
 # ifdef _GLIBCXX_HAVE_TLS
@@ -814,7 +829,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     void
     call_once(once_flag& __once, _Callable&& __f, _Args&&... __args)
     {
-#if defined _GLIBCXX_HAVE_LINUX_FUTEX || ! defined _GLIBCXX_HAS_GTHREADS
+#if defined _GLIBCXX_HAVE_LINUX_FUTEX || ! defined _GLIBCXX_HAS_GTHREADS \
+      || _GLIBCXX_COMPAT_PTHREAD_ONCE_T
       if (__once._M_passive())
 	return;
       else if (__once._M_activate())
diff --git a/libstdc++-v3/src/c++11/mutex.cc b/libstdc++-v3/src/c++11/mutex.cc
index 286f77f9a454..e63b709749a6 100644
--- a/libstdc++-v3/src/c++11/mutex.cc
+++ b/libstdc++-v3/src/c++11/mutex.cc
@@ -82,6 +82,26 @@ std::once_flag::_M_finish(bool returning) noexcept
     }
 }
 
+#elif defined _GLIBCXX_COMPAT_PTHREAD_ONCE_T
+
+bool
+std::once_flag::_M_activate()
+{
+  pthread_mutex_lock(&_M_once._M_mutex);
+  if (_M_once._M_done == 0)
+    return true;
+  pthread_mutex_unlock(&_M_once._M_mutex);
+  return false;
+}
+
+void
+std::once_flag::_M_finish(bool returning) noexcept
+{
+  if (returning)
+    _M_once._M_done = 1;
+  pthread_mutex_unlock(&_M_once._M_mutex);
+}
+
 #endif // ! FUTEX
 
 #ifndef _GLIBCXX_HAVE_TLS