--- Modules/_ctypes/libffi_osx/x86/x86-ffi64.c
+++ Modules/_ctypes/libffi_osx/x86/x86-ffi64.c
@@ -599,9 +599,15 @@
 	tramp = (volatile unsigned short*)&closure->tramp[0];
 
 	tramp[0] = 0xbb49;		/* mov <code>, %r11	*/
-	*(void* volatile*)&tramp[1] = ffi_closure_unix64;
+	tramp[1] = (unsigned short) ffi_closure_unix64;
+	tramp[2] = (unsigned short) (((unsigned long)ffi_closure_unix64) >> 16);
+	tramp[3] = (unsigned short) (((unsigned long)ffi_closure_unix64) >> 32);
+	tramp[4] = (unsigned short) (((unsigned long)ffi_closure_unix64) >> 48);
 	tramp[5] = 0xba49;		/* mov <data>, %r10	*/
-	*(void* volatile*)&tramp[6] = closure;
+	tramp[6] = (unsigned short) closure;
+	tramp[7] = (unsigned short) (((unsigned long)closure) >> 16);
+	tramp[8] = (unsigned short) (((unsigned long)closure) >> 32);
+	tramp[9] = (unsigned short) (((unsigned long)closure) >> 48);
 
 	/*	Set the carry bit if the function uses any sse registers.
 		This is clc or stc, together with the first byte of the jmp.  */