diff --git a/drivers/net/dsa/mv88e6xxx/ptp.c b/drivers/net/dsa/mv88e6xxx/ptp.c
index 076e622a64d6..3b1985902f95 100644
--- a/drivers/net/dsa/mv88e6xxx/ptp.c
+++ b/drivers/net/dsa/mv88e6xxx/ptp.c
@@ -276,7 +276,8 @@ static int mv88e6352_ptp_enable_extts(struct mv88e6xxx_chip *chip,
 	/* Reject requests with unsupported flags */
 	if (rq->extts.flags & ~(PTP_ENABLE_FEATURE |
 				PTP_RISING_EDGE |
-				PTP_FALLING_EDGE))
+				PTP_FALLING_EDGE |
+				PTP_STRICT_FLAGS))
 		return -EOPNOTSUPP;
 
 	pin = ptp_find_pin(chip->ptp_clock, PTP_PF_EXTTS, rq->extts.index);
diff --git a/drivers/net/ethernet/intel/igb/igb_ptp.c b/drivers/net/ethernet/intel/igb/igb_ptp.c
index 0bce3e0f1af0..3fd60715bca7 100644
--- a/drivers/net/ethernet/intel/igb/igb_ptp.c
+++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
@@ -524,7 +524,8 @@ static int igb_ptp_feature_enable_i210(struct ptp_clock_info *ptp,
 		/* Reject requests with unsupported flags */
 		if (rq->extts.flags & ~(PTP_ENABLE_FEATURE |
 					PTP_RISING_EDGE |
-					PTP_FALLING_EDGE))
+					PTP_FALLING_EDGE |
+					PTP_STRICT_FLAGS))
 			return -EOPNOTSUPP;
 
 		if (on) {
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
index 9a40f24e3193..819097d9b583 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/lib/clock.c
@@ -239,7 +239,8 @@ static int mlx5_extts_configure(struct ptp_clock_info *ptp,
 	/* Reject requests with unsupported flags */
 	if (rq->extts.flags & ~(PTP_ENABLE_FEATURE |
 				PTP_RISING_EDGE |
-				PTP_FALLING_EDGE))
+				PTP_FALLING_EDGE |
+				PTP_STRICT_FLAGS))
 		return -EOPNOTSUPP;
 
 	if (rq->extts.index >= clock->ptp_info.n_pins)
diff --git a/drivers/net/ethernet/renesas/ravb_ptp.c b/drivers/net/ethernet/renesas/ravb_ptp.c
index 666dbee48097..6984bd5b7da9 100644
--- a/drivers/net/ethernet/renesas/ravb_ptp.c
+++ b/drivers/net/ethernet/renesas/ravb_ptp.c
@@ -185,7 +185,8 @@ static int ravb_ptp_extts(struct ptp_clock_info *ptp,
 	/* Reject requests with unsupported flags */
 	if (req->flags & ~(PTP_ENABLE_FEATURE |
 			   PTP_RISING_EDGE |
-			   PTP_FALLING_EDGE))
+			   PTP_FALLING_EDGE |
+			   PTP_STRICT_FLAGS))
 		return -EOPNOTSUPP;
 
 	if (req->index)
diff --git a/drivers/net/phy/dp83640.c b/drivers/net/phy/dp83640.c
index 2781b0e2d947..3bba2bea3a88 100644
--- a/drivers/net/phy/dp83640.c
+++ b/drivers/net/phy/dp83640.c
@@ -472,7 +472,8 @@ static int ptp_dp83640_enable(struct ptp_clock_info *ptp,
 		/* Reject requests with unsupported flags */
 		if (rq->extts.flags & ~(PTP_ENABLE_FEATURE |
 					PTP_RISING_EDGE |
-					PTP_FALLING_EDGE))
+					PTP_FALLING_EDGE |
+					PTP_STRICT_FLAGS))
 			return -EOPNOTSUPP;
 		index = rq->extts.index;
 		if (index >= N_EXT_TS)
diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index cbbe1237ff8d..9d72ab593f13 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -150,6 +150,8 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 			break;
 		}
 		if (cmd == PTP_EXTTS_REQUEST2) {
+			/* Tell the drivers to check the flags carefully. */
+			req.extts.flags |= PTP_STRICT_FLAGS;
 			/* Make sure no reserved bit is set. */
 			if ((req.extts.flags & ~PTP_EXTTS_VALID_FLAGS) ||
 			    req.extts.rsv[0] || req.extts.rsv[1]) {
diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h
index 304059b1609d..9dc9d0079e98 100644
--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h
@@ -31,6 +31,7 @@
 #define PTP_ENABLE_FEATURE (1<<0)
 #define PTP_RISING_EDGE    (1<<1)
 #define PTP_FALLING_EDGE   (1<<2)
+#define PTP_STRICT_FLAGS   (1<<3)
 #define PTP_EXTTS_EDGES    (PTP_RISING_EDGE | PTP_FALLING_EDGE)
 
 /*
@@ -38,7 +39,8 @@
  */
 #define PTP_EXTTS_VALID_FLAGS	(PTP_ENABLE_FEATURE |	\
 				 PTP_RISING_EDGE |	\
-				 PTP_FALLING_EDGE)
+				 PTP_FALLING_EDGE |	\
+				 PTP_STRICT_FLAGS)
 
 /*
  * flag fields valid for the original PTP_EXTTS_REQUEST ioctl.