diff --git a/core-functions.md b/core-functions.md
index 74aa4d3..ae9f4dd 100644
--- a/core-functions.md
+++ b/core-functions.md
@@ -6,7 +6,7 @@ Public. Takes an arbitrary number of arguments. Returns true if all are readable
 
 # (atom? arg)
 
-Public. Takes one argument. Returns TRUE if that argument is neither a CONS cell nor a STRG cell, else NIL.
+Public. Takes one argument. Returns TRUE if that argument is neither a CONS cell, a VECP, nor a STRG cell, else NIL.
 
 # (append args...)