Fixed a loop bug.  This fixes #100
diff --git a/jinja2/compiler.py b/jinja2/compiler.py
index 59d770f..02df8c5 100644
--- a/jinja2/compiler.py
+++ b/jinja2/compiler.py
@@ -1066,6 +1066,7 @@
         # make sure the loop variable is a special one and raise a template
         # assertion error if a loop tries to write to loop
         if extended_loop:
+            self.writeline('l_loop = missing')
             loop_frame.identifiers.add_special('loop')
         for name in node.find_all(nodes.Name):
             if name.ctx == 'store' and name.name == 'loop':