diff --git a/src/x86/win64.S b/src/x86/win64.S
index a5a20b64..eed57c21 100644
--- a/src/x86/win64.S
+++ b/src/x86/win64.S
@@ -7,10 +7,19 @@
         .cfi_sections   .debug_frame
 #endif
 
+#ifdef X86_WIN64
+#define SEH(...) __VA_ARGS__
 #define arg0	%rcx
 #define arg1	%rdx
 #define arg2	%r8
 #define arg3	%r9
+#else
+#define SEH(...)
+#define arg0	%rdi
+#define arg1	%rsi
+#define arg2	%rdx
+#define arg3	%rcx
+#endif
 
 #ifdef SYMBOL_UNDERSCORE
 #define SYMBOL_NAME(name) _##name
@@ -34,7 +43,7 @@
 	.align	8
 	.globl	ffi_call_win64
 
-	.seh_proc ffi_call_win64
+	SEH(.seh_proc ffi_call_win64)
 ffi_call_win64:
 	cfi_startproc
 	/* Set up the local stack frame and install it in rbp/rsp.  */
@@ -44,9 +53,9 @@ ffi_call_win64:
 	movq	arg1, %rbp
 	cfi_def_cfa(%rbp, 16)
 	cfi_rel_offset(%rbp, 0)
-	.seh_pushreg %rbp
-	.seh_setframe %rbp, 0
-	.seh_endprologue
+	SEH(.seh_pushreg %rbp)
+	SEH(.seh_setframe %rbp, 0)
+	SEH(.seh_endprologue)
 	movq	arg0, %rsp
 
 	movq	arg2, %r10
@@ -149,7 +158,7 @@ E FFI_TYPE_SMALL_STRUCT_4B
 .purgem epilogue
 
 	cfi_endproc
-	.seh_endproc
+	SEH(.seh_endproc)
 
 
 /* 32 bytes of outgoing register stack space, 8 bytes of alignment,
@@ -161,33 +170,33 @@ E FFI_TYPE_SMALL_STRUCT_4B
 	.align	8
 	.globl	ffi_go_closure_win64
 
-	.seh_proc ffi_go_closure_win64
+	SEH(.seh_proc ffi_go_closure_win64)
 ffi_go_closure_win64:
 	cfi_startproc
 	/* Save all integer arguments into the incoming reg stack space.  */
-	movq	arg0, 8(%rsp)
-	movq	arg1, 16(%rsp)
-	movq	arg2, 24(%rsp)
-	movq	arg3, 32(%rsp)
+	movq	%rcx, 8(%rsp)
+	movq	%rdx, 16(%rsp)
+	movq	%r8, 24(%rsp)
+	movq	%r9, 32(%rsp)
 
 	movq	8(%r10), arg0			/* load cif */
 	movq	16(%r10), arg1			/* load fun */
 	movq	%r10, arg2			/* closure is user_data */
 	jmp	0f
 	cfi_endproc
-	.seh_endproc
+	SEH(.seh_endproc)
 
 	.align	8
 	.globl	ffi_closure_win64
 
-	.seh_proc ffi_closure_win64
+	SEH(.seh_proc ffi_closure_win64)
 ffi_closure_win64:
 	cfi_startproc
 	/* Save all integer arguments into the incoming reg stack space.  */
-	movq	arg0, 8(%rsp)
-	movq	arg1, 16(%rsp)
-	movq	arg2, 24(%rsp)
-	movq	arg3, 32(%rsp)
+	movq	%rcx, 8(%rsp)
+	movq	%rdx, 16(%rsp)
+	movq	%r8, 24(%rsp)
+	movq	%r9, 32(%rsp)
 
 	movq	FFI_TRAMPOLINE_SIZE(%r10), arg0		/* load cif */
 	movq	FFI_TRAMPOLINE_SIZE+8(%r10), arg1	/* load fun */
@@ -195,8 +204,8 @@ ffi_closure_win64:
 0:
 	subq	$ffi_clo_FS, %rsp
 	cfi_adjust_cfa_offset(ffi_clo_FS)
-	.seh_stackalloc ffi_clo_FS
-	.seh_endprologue
+	SEH(.seh_stackalloc ffi_clo_FS)
+	SEH(.seh_endprologue)
 
 	/* Save all sse arguments into the stack frame.  */
 	movsd	%xmm0, ffi_clo_OFF_X(%rsp)
@@ -216,4 +225,4 @@ ffi_closure_win64:
 	ret
 
 	cfi_endproc
-	.seh_endproc
+	SEH(.seh_endproc)