diff --git a/mode/perl.py b/mode/perl.py
index 0868fc7..513318c 100644
--- a/mode/perl.py
+++ b/mode/perl.py
@@ -755,6 +755,9 @@ class Perl(mode.Fundamental):
     def get_line_function(self, y):
         if self.funclines is None:
             self.build_function_map()
-        return self.funclines[y]
+        if y < len(self.funclines):
+            return self.funclines[y]
+        else:
+            return None
 
 install = Perl.install