diff --git a/pandas/io/excel.py b/pandas/io/excel.py
index 36af8b1da0e30..82ad17258113f 100644
--- a/pandas/io/excel.py
+++ b/pandas/io/excel.py
@@ -622,7 +622,7 @@ def _convert_to_style(cls, style_dict):
 if openpyxl_compat.is_compat():
     register_writer(_OpenpyxlWriter)
 else:
-    warn('Installed openpyxl is not supported at this time. Use >={} and <{}.'
+    warn('Installed openpyxl is not supported at this time. Use >={0} and <{1}.'
             .format(openpyxl_compat.start_ver, openpyxl_compat.stop_ver))