diff --git a/overviewer_core/optimizeimages.py b/overviewer_core/optimizeimages.py
index f3d9631..8d99581 100644
--- a/overviewer_core/optimizeimages.py
+++ b/overviewer_core/optimizeimages.py
@@ -125,7 +125,7 @@ class advpng(Optimizer, PNGOptimizer):
     binaryname = "advpng"
     crusher = True
 
-    def __init__(self, olevel=3)
+    def __init__(self, olevel=3):
         self.olevel = olevel
 
     def optimize(self, img):