diff --git a/tools/vrepl.v b/tools/vrepl.v
index 3b445aa9d2..b1b8c02e0b 100644
--- a/tools/vrepl.v
+++ b/tools/vrepl.v
@@ -122,12 +122,12 @@ pub fn run_repl() []string {
 		}
 		was_func := r.in_func
 		if r.checks() {
-			for line in r.line.split('\n') {
+			for rline in r.line.split('\n') {
 				if r.in_func || was_func {
-					r.functions << line
+					r.functions << rline
 				}
 				else {
-					r.temp_lines << line
+					r.temp_lines << rline
 				}
 			}
 			if r.indent > 0 {
diff --git a/tutorials/building-a-simple-web-blog-with-vweb.md b/tutorials/building-a-simple-web-blog-with-vweb.md
index 56bd27a35f..58431fd3c3 100644
--- a/tutorials/building-a-simple-web-blog-with-vweb.md
+++ b/tutorials/building-a-simple-web-blog-with-vweb.md
@@ -247,7 +247,7 @@ struct Article {
 	text  string
 }
 
-pub fn (app & App) find_all_articles() []Article {
+pub fn (app &App) find_all_articles() []Article {
 	db := app.db
 	articles := db.select from Article
 	return articles
@@ -314,8 +314,8 @@ article := app.retrieve_article(10) or {
 ```
 
 
-> Temporary variables like `db := app.db` are a temporary limitation in the
-V ORM, soon they will not be needed.
+> `db := app.db` is a temporary limitation in the
+V ORM, soon this will not be needed.
 
 To be continued on Dec 14...
 
diff --git a/vlib/compiler/for.v b/vlib/compiler/for.v
index fc9a1f0633..5badadfaf2 100644
--- a/vlib/compiler/for.v
+++ b/vlib/compiler/for.v
@@ -103,6 +103,9 @@ fn (p mut Parser) for_st() {
 		}
 		// Register temp vars
 		if i != '_' {
+			if p.known_var(i) {
+				p.error('redefinition of `$i`')
+			}
 			p.register_var(Var {
 				name: i
 				typ: i_var_type
@@ -111,6 +114,9 @@ fn (p mut Parser) for_st() {
 			})
 		}
 		if val != '_' {
+			if p.known_var(val) {
+				p.error('redefinition of `$val`')
+			}
 			p.register_var(Var {
 				name: val
 				typ: typ
@@ -182,6 +188,9 @@ fn (p mut Parser) for_st() {
 		// println('for typ=$typ vartyp=$var_typ')
 		// Register temp var
 		if val != '_' {
+			if p.known_var(val) {
+				p.error('redefinition of `$val`')
+			}
 			p.register_var(Var {
 				name: val
 				typ: typ