diff --git a/EIPS/eip-663.md b/EIPS/eip-663.md
index ef01840095254..b8ae76e96466d 100644
--- a/EIPS/eip-663.md
+++ b/EIPS/eip-663.md
@@ -29,8 +29,8 @@ Introducing `SWAPN` and `DUPN` will provide an option to compilers to simplify a
 
 We introduce two new instructions:
 
- 1. `DUPN` (`0xb0`)
- 2. `SWAPN` (`0xb1`)
+ 1. `DUPN` (`0xb3`)
+ 2. `SWAPN` (`0xb4`)
 
 If the code is legacy bytecode, both of these instructions result in an *exceptional halt*. (*Note: This means no change to behaviour.*)
 
@@ -61,7 +61,7 @@ TBA
 
 ## Security Considerations
 
-TBA
+The authors are not aware of any additional risks introduced here. The EVM stack is fixed at 1024 items and most implementations keep that in memory at all times. This change will increase the easy-to-access number of items from 16 to 256.
 
 ## Copyright