diff --git a/panoramix/forms.py b/panoramix/forms.py
index 3527598024b9b..c59f9cb0f329a 100644
--- a/panoramix/forms.py
+++ b/panoramix/forms.py
@@ -131,7 +131,9 @@ def __init__(self, viz):
             'compare_suffix': TextField('Comparison suffix',
                 description="Suffix to apply after the percentage display"),
             'y_axis_format': TextField('Y axis format',
-                description="D3 format syntax for y axis"),
+                description="D3 format syntax for y axis "
+                            "https://github.com/mbostock/\n"
+                            "d3/wiki/Formatting"),
             'markup_type': SelectField(
                 "Markup Type",
                 choices=self.choicify(['markdown', 'html']),