diff --git a/pixelsnap.py b/pixelsnap.py
index dcedb40f64bd887983c62714a9a5832ac0885e4a..649b33bd2d697ece525620cb2f8c8eae21f59de5 100755
--- a/pixelsnap.py
+++ b/pixelsnap.py
@@ -132,7 +132,7 @@ class PixelSnap(inkex.EffectExtension):
             "--max_gradient",
             type=float,
             default=0.5,
-            help="Maximum slope to consider straight (%)",
+            help="Maximum slope to consider straight (%%)",
         )
         pars.add_argument(
             "-s",