diff --git a/4.2.md b/4.2.md
index 6a63af4c..9113fb05 100644
--- a/4.2.md
+++ b/4.2.md
@@ -124,7 +124,7 @@
 
 	slice:=[]string{"football","basketball","tennis"}
 	a:=Slice_diff(r.Form["interest"],slice)
-	if a = nil{
+	if a == nil{
 		return true
 	}