diff --git a/plat/rockchip/rk3368/drivers/ddr/ddr_rk3368.c b/plat/rockchip/rk3368/drivers/ddr/ddr_rk3368.c
index 84d2654..fa98eb3 100644
--- a/plat/rockchip/rk3368/drivers/ddr/ddr_rk3368.c
+++ b/plat/rockchip/rk3368/drivers/ddr/ddr_rk3368.c
@@ -400,7 +400,7 @@
 		p_ddr_reg->dpllcon[0] = (mmio_read_32(CRU_BASE +
 						      PLL_CONS(DPLL_ID, 0))
 							& 0xffff) |
-					(0xFFFF << 16);
+					(0xFFFFu << 16);
 		p_ddr_reg->dpllcon[1] = (mmio_read_32(CRU_BASE +
 						      PLL_CONS(DPLL_ID, 1))
 							& 0xffff);
@@ -410,7 +410,7 @@
 		p_ddr_reg->dpllcon[3] = (mmio_read_32(CRU_BASE +
 						      PLL_CONS(DPLL_ID, 3))
 							& 0xffff) |
-					(0xFFFF << 16);
+					(0xFFFFu << 16);
 	} else {
 		ddr_get_dpll_cfg(&p_ddr_reg->dpllcon[0]);
 	}