diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
index 764832f4dae1..8b50f03056b7 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c
@@ -47,7 +47,8 @@ static void config_sub_second_increment(void __iomem *ioaddr,
 	if (!(value & PTP_TCR_TSCTRLSSR))
 		data = (data * 1000) / 465;
 
-	data &= PTP_SSIR_SSINC_MASK;
+	if (data > PTP_SSIR_SSINC_MAX)
+		data = PTP_SSIR_SSINC_MAX;
 
 	reg_value = data;
 	if (gmac4)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
index 53172a439810..bf619295d079 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.h
@@ -64,7 +64,7 @@
 #define	PTP_TCR_TSENMACADDR	BIT(18)
 
 /* SSIR defines */
-#define	PTP_SSIR_SSINC_MASK		0xff
+#define	PTP_SSIR_SSINC_MAX		0xff
 #define	GMAC4_PTP_SSIR_SSINC_SHIFT	16
 
 /* Auxiliary Control defines */