diff --git a/README.md b/README.md
index 3444839..f3a4f99 100644
--- a/README.md
+++ b/README.md
@@ -190,9 +190,11 @@
 See the git log for details at http://github.com/libffi/libffi.
 
     3.3 TBD
+        Default to Microsoft's 64 bit long double ABI with Visual C++.
+	  GNU compiler uses 80 bits (128 in memory) FFI_GNUW64 ABI.
         New API in support of GO closures.
         Add RISC-V support.
-	Many bug fixes.
+        Many bug fixes.
     
     3.2.1 Nov-12-14
         Build fix for non-iOS AArch64 targets.
diff --git a/src/x86/ffitarget.h b/src/x86/ffitarget.h
index 25e3f4f..3a0efa5 100644
--- a/src/x86/ffitarget.h
+++ b/src/x86/ffitarget.h
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------*-C-*-
-   ffitarget.h - Copyright (c) 2012, 2014  Anthony Green
+   ffitarget.h - Copyright (c) 2012, 2014, 2018  Anthony Green
                  Copyright (c) 1996-2003, 2010  Red Hat, Inc.
                  Copyright (C) 2008  Free Software Foundation, Inc.
 
@@ -80,9 +80,14 @@
 typedef enum ffi_abi {
 #if defined(X86_WIN64)
   FFI_FIRST_ABI = 0,
-  FFI_WIN64,
+  FFI_WIN64,            /* sizeof(long double) == 8  - microsoft compilers */
+  FFI_GNUW64,           /* sizeof(long double) == 16 - GNU compilers */
   FFI_LAST_ABI,
+#ifdef __GNUC__
+  FFI_DEFAULT_ABI = FFI_GNUW64
+#else  
   FFI_DEFAULT_ABI = FFI_WIN64
+#endif  
 
 #elif defined(X86_64) || (defined (__x86_64__) && defined (X86_DARWIN))
   FFI_FIRST_ABI = 1,
diff --git a/src/x86/ffiw64.c b/src/x86/ffiw64.c
index fd47c58..f787525 100644
--- a/src/x86/ffiw64.c
+++ b/src/x86/ffiw64.c
@@ -1,5 +1,6 @@
 /* -----------------------------------------------------------------------
-   ffiw64.c - Copyright (c) 2014 Red Hat, Inc.
+   ffiw64.c - Copyright (c) 2018 Anthony Green
+              Copyright (c) 2014 Red Hat, Inc.
 
    x86 win64 Foreign Function Interface
 
@@ -52,8 +53,14 @@
 {
   int flags, n;
 
-  if (cif->abi != FFI_WIN64)
-    return FFI_BAD_ABI;
+  switch (cif->abi)
+    {
+    case FFI_WIN64:
+    case FFI_GNUW64:
+      break;
+    default:
+      return FFI_BAD_ABI;
+    }
 
   flags = cif->rtype->type;
   switch (flags)
@@ -61,7 +68,9 @@
     default:
       break;
     case FFI_TYPE_LONGDOUBLE:
-      flags = FFI_TYPE_STRUCT;
+      /* GCC returns long double values by reference, like a struct */
+      if (cif->abi == FFI_GNUW64)
+	flags = FFI_TYPE_STRUCT;
       break;
     case FFI_TYPE_COMPLEX:
       flags = FFI_TYPE_STRUCT;
@@ -106,7 +115,7 @@
   size_t rsize;
   struct win64_call_frame *frame;
 
-  FFI_ASSERT(cif->abi == FFI_WIN64);
+  FFI_ASSERT(cif->abi == FFI_GNUW64 || cif->abi == FFI_WIN64);
 
   flags = cif->flags;
   rsize = 0;
@@ -196,8 +205,14 @@
   };
   char *tramp = closure->tramp;
 
-  if (cif->abi != FFI_WIN64)
-    return FFI_BAD_ABI;
+  switch (cif->abi)
+    {
+    case FFI_WIN64:
+    case FFI_GNUW64:
+      break;
+    default:
+      return FFI_BAD_ABI;
+    }
 
   memcpy (tramp, trampoline, sizeof(trampoline));
   *(UINT64 *)(tramp + 16) = (uintptr_t)ffi_closure_win64;
@@ -213,8 +228,14 @@
 EFI64(ffi_prep_go_closure)(ffi_go_closure* closure, ffi_cif* cif,
 		     void (*fun)(ffi_cif*, void*, void**, void*))
 {
-  if (cif->abi != FFI_WIN64)
-    return FFI_BAD_ABI;
+  switch (cif->abi)
+    {
+    case FFI_WIN64:
+    case FFI_GNUW64:
+      break;
+    default:
+      return FFI_BAD_ABI;
+    }
 
   closure->tramp = ffi_go_closure_win64;
   closure->cif = cif;