diff --git a/clash-cores/src/Clash/Cores/Sgmii/BitSlip.hs b/clash-cores/src/Clash/Cores/Sgmii/BitSlip.hs
index 36f4a5cd87..c33a15d00f 100644
--- a/clash-cores/src/Clash/Cores/Sgmii/BitSlip.hs
+++ b/clash-cores/src/Clash/Cores/Sgmii/BitSlip.hs
@@ -62,7 +62,7 @@ bitSlipT BSFail{..} (cg, _)
 
   n = elemIndex True $ map f _hist
    where
-    f a = a == 0b1111100 || a == 0b0000011
+    f a = a == 0b0011111 || a == 0b1100000
 bitSlipT BSOk{..} (cg, syncStatus)
   | failTimer >= timeout (Proxy @dom) = BSFail s (repeat 0) (repeat 0)
   | otherwise = BSOk s _n failTimer