diff --git a/clutter/clutter-fixed.c b/clutter/clutter-fixed.c
index 6c254cb3b..f7d46da48 100644
--- a/clutter/clutter-fixed.c
+++ b/clutter/clutter-fixed.c
@@ -222,7 +222,7 @@ clutter_sini (ClutterAngle angle)
     }
     
     /* reduce to <0, 2*pi) */
-    angle &= 0x7ff;
+    angle &= 0x3ff;
     
     /* reduce to first quadrant and sign */
     if (angle > 512)