diff --git a/test_tablib.py b/test_tablib.py
index 1391097..692426d 100755
--- a/test_tablib.py
+++ b/test_tablib.py
@@ -176,15 +176,15 @@ class TablibTestCase(unittest.TestCase):
         """Verify getting columns by index"""
 
         self.assertEqual(
-            self.founders.get_col(self.headers.index('first_name')),
+            self.founders.get_col(list(self.headers).index('first_name')),
             [self.john[0], self.george[0], self.tom[0]])
 
         self.assertEqual(
-            self.founders.get_col(self.headers.index('last_name')),
+            self.founders.get_col(list(self.headers).index('last_name')),
             [self.john[1], self.george[1], self.tom[1]])
 
         self.assertEqual(
-            self.founders.get_col(self.headers.index('gpa')),
+            self.founders.get_col(list(self.headers).index('gpa')),
             [self.john[2], self.george[2], self.tom[2]])