diff --git a/dynasm/dasm_x86.lua b/dynasm/dasm_x86.lua
index 1f0981f3..07ddd98d 100644
--- a/dynasm/dasm_x86.lua
+++ b/dynasm/dasm_x86.lua
@@ -1040,7 +1040,7 @@ local map_op = {
   -- ED: *in Rdw,dx
   -- EE: *out dx,Rb
   -- EF: *out dx,Rdw
-  -- F0: *lock
+  lock_0 =	"F0",
   int1_0 =	"F1",
   repne_0 =	"F2",
   repnz_0 =	"F2",