diff --git a/x86_64/6_clib.asm b/x86_64/6_clib.asm
index 70f968c..b167d3c 100644
--- a/x86_64/6_clib.asm
+++ b/x86_64/6_clib.asm
@@ -29,6 +29,9 @@ main:
 
 	; This segfaults when moved below the line "jne .fail"
 	; Why?
+	; Because it stores the float registers on the stack
+	; as well. This doesn't seem to be particularly well
+	; documented.
 	sub rsp, 8 ; allocate 8 bytes = 2 integers
 
 	cmp r12, 3 ; argc == 3