diff --git a/Known-issues.md b/Known-issues.md
index 6417755..bc41f98 100644
--- a/Known-issues.md
+++ b/Known-issues.md
@@ -16,6 +16,7 @@
 
 ### I/O
 
+ * Using `-exec` argument without `-io` disables all I/O emulation modules.
  * `Insert Coin` action is not implemented in all I/O emulation modules. Some older systems omit this. You should instead be using the `Service` button, which *is* implemented in all I/O modules.
  * `Insert Coin` and `Service` may be prevented due to "coin strip" - some data release groups in the past ripped out the code that handles coins to discourage people from running data in real arcades. Get a clean DLL to fix this, or enable Free Play instead.
  * In a real arcade, a "coin blocker" physically prevents coins from being inserted. This would be enabled by the game if you set shop closing hours in the test menu.