diff --git a/vlib/v/parser/for.v b/vlib/v/parser/for.v
index 788162904b..2cdebd9324 100644
--- a/vlib/v/parser/for.v
+++ b/vlib/v/parser/for.v
@@ -73,6 +73,9 @@ fn (mut p Parser) for_stmt() ast.Stmt {
 			key_var_name = val_var_name
 			val_var_pos = p.tok.position()
 			val_var_name = p.check_name()
+			if key_var_name == val_var_name {
+				p.error_with_pos('key and value in a for loop cannot be the same', val_var_pos)
+			}
 			if p.scope.known_var(key_var_name) {
 				p.error('redefinition of key iteration variable `$key_var_name`')
 			}