diff -ru python3.orig/Modules/_ctypes/libffi/src/x86/ffi64.c python3/Modules/_ctypes/libffi/src/x86/ffi64.c
--- Modules/_ctypes/libffi/src/x86/ffi64.c	2015-07-05 18:50:07.000000000 +0200
+++ Modules/_ctypes/libffi/src/x86/ffi64.c	2015-07-26 20:18:56.457153323 +0200
@@ -548,11 +548,15 @@
   tramp = (volatile unsigned short *) &closure->tramp[0];
 
   tramp[0] = 0xbb49;		/* mov <code>, %r11	*/
-  *((unsigned long long * volatile) &tramp[1])
-    = (unsigned long) ffi_closure_unix64;
+  tramp[1] = (unsigned long) ffi_closure_unix64;
+  tramp[2] = ((unsigned long) ffi_closure_unix64) >> 16;
+  tramp[3] = ((unsigned long) ffi_closure_unix64) >> 32;
+  tramp[4] = ((unsigned long) ffi_closure_unix64) >> 48;
   tramp[5] = 0xba49;		/* mov <data>, %r10	*/
-  *((unsigned long long * volatile) &tramp[6])
-    = (unsigned long) codeloc;
+  tramp[6] = (unsigned long) codeloc;
+  tramp[7] = ((unsigned long) codeloc) >> 16;
+  tramp[8] = ((unsigned long) codeloc) >> 32;
+  tramp[9] = ((unsigned long) codeloc) >> 48;
 
   /* Set the carry bit iff the function uses any sse registers.
      This is clc or stc, together with the first byte of the jmp.  */