diff --git a/eBook/18.1.md b/eBook/18.1.md
index b6c467d..ae1cf9e 100644
--- a/eBook/18.1.md
+++ b/eBook/18.1.md
@@ -4,7 +4,7 @@
 
 ```go
 str:="hello"
-c:=[]byte(s)
+c:=[]byte(str)
 c[0]='c'
 s2:= string(c) // s2 == "cello"
 ```