diff --git a/netutils/ptpd/Kconfig b/netutils/ptpd/Kconfig
index b27143ba2..0bd2389fd 100644
--- a/netutils/ptpd/Kconfig
+++ b/netutils/ptpd/Kconfig
@@ -175,6 +175,26 @@ config NETUTILS_PTPD_DRIFT_AVERAGE_S
 		gives more stable estimate but reacts slower to crystal oscillator speed
 		changes (such as caused by temperature changes).
 
+config NETUTILS_PTPD_MAX_DRIFT_PPB
+	int "PTP client maximum plausible clock drift rate (ppb)"
+	default 500000
+	range 1000 20000000
+	---help---
+		A single drift-rate sample computed between two consecutive sync
+		updates is discarded (the previous averaged drift_ppb is kept
+		unchanged) if its magnitude exceeds this bound. Real crystal
+		oscillators drift by at most a few hundred ppm (hundreds of
+		thousands of ppb), so this catches bogus samples caused by an
+		abnormally short or long measurement interval - e.g. right after
+		a clock source outage/reconnect, or a burst of closely spaced
+		sync packets following packet loss - before they corrupt the
+		long-term drift_ppb average and get applied to the hardware.
+
+		This is intentionally much tighter than
+		CLOCK_ADJTIME_SLEWLIMIT_PPM, which bounds how fast a correction
+		may be applied rather than how large a real drift measurement
+		can plausibly be.
+
 config NETUTILS_PTPD_MAX_PATH_DELAY_NS
 	int "PTP client maximum path delay (ns)"
 	default 100000
diff --git a/netutils/ptpd/ptpd.c b/netutils/ptpd/ptpd.c
index 162ba98f7..23b2180d5 100644
--- a/netutils/ptpd/ptpd.c
+++ b/netutils/ptpd/ptpd.c
@@ -1232,8 +1232,6 @@ static int ptp_update_local_clock(FAR struct ptp_state_s *state,
       const int64_t max_adjust_ns =
         (int64_t)CONFIG_CLOCK_ADJTIME_SLEWLIMIT_PPM *
         CONFIG_CLOCK_ADJTIME_PERIOD_MS;
-      const int64_t slew_limit_ppb =
-        (int64_t)CONFIG_CLOCK_ADJTIME_SLEWLIMIT_PPM * 1000;
 
       if (!state->has_last_delta)
         {
@@ -1269,8 +1267,19 @@ static int ptp_update_local_clock(FAR struct ptp_state_s *state,
               interval_ms = 1;
             }
 
-          if (drift_ppb > slew_limit_ppb || drift_ppb < -slew_limit_ppb)
+          if (drift_ppb > CONFIG_NETUTILS_PTPD_MAX_DRIFT_PPB ||
+              drift_ppb < -CONFIG_NETUTILS_PTPD_MAX_DRIFT_PPB)
             {
+              /* Physically implausible for a real crystal oscillator -
+               * almost always the result of an abnormally short interval
+               * between samples (e.g. a burst of packets right after a
+               * clock source outage/reconnect) rather than actual drift.
+               * Discard it instead of letting it corrupt the long-term
+               * average; CLOCK_ADJTIME_SLEWLIMIT_PPM is a much looser
+               * hardware safety bound and would let this through
+               * unchanged.
+               */
+
               ptpwarn("Drift estimate out of range: %lld\n",
                       (long long)drift_ppb);
               drift_ppb = state->drift_ppb;