diff --git a/libs/ardour/sse_functions_64bit_win.s b/libs/ardour/sse_functions_64bit_win.s
index 7a50c9aef5..78c50930c2 100644
--- a/libs/ardour/sse_functions_64bit_win.s
+++ b/libs/ardour/sse_functions_64bit_win.s
@@ -629,7 +629,7 @@ x86_sse_compute_peak:
 
 	addq $16, %rdi
 
-	subq $4, %rdx #; nframes-=4
+	subq $4, %rcx #; nframes-=4
 
 	decq %rax
 	jnz .LP_SSE