diff --git a/subsys/bluetooth/controller/Kconfig.ll_sw_split b/subsys/bluetooth/controller/Kconfig.ll_sw_split
index d5028b157d8c7cc..1f667987f2fda38 100644
--- a/subsys/bluetooth/controller/Kconfig.ll_sw_split
+++ b/subsys/bluetooth/controller/Kconfig.ll_sw_split
@@ -106,6 +106,7 @@ config BT_CTLR_ULL_LLL_PRIO_SUPPORT
 
 choice BT_LL_SW_LLCP_IMPL
 	prompt "Bluetooth Low Energy Software Link Layer Control Procedure Implementation"
+	default BT_LL_SW_LLCP_LEGACY if SOC_SERIES_NRF51X
 	default BT_LL_SW_LLCP
 	help
 	  Select the Bluetooth Low Energy Software Link Layer Control Procedure implementation.