diff --git a/clients/upsmon.c b/clients/upsmon.c
index 39c61ba6dc..a08a453888 100644
--- a/clients/upsmon.c
+++ b/clients/upsmon.c
@@ -657,6 +657,19 @@ static int is_ups_critical(utype_t *ups)
 
 	/* must be OB+LB now */
 
+	/* if UPS is calibrating, don't declare it critical */
+	/* FIXME: Consider UPSes where we can know if they have other power
+	 * circuits (bypass, etc.) and whether those do currently provide
+	 * wall power to the host - and that we do not have both calibration
+	 * and a real outage, when we still should shut down right now.
+	 */
+	if (flag_isset(ups->status, ST_CAL)) {
+		upslogx(LOG_WARNING, "%s: seems that UPS [%s] is OB+LB now, but "
+			"it is also calibrating - not declaring a critical state",
+			  __func__, ups->upsname);
+		return 0;
+	}
+
 	/* if we're a master, declare it critical so we set FSD on it */
 	if (flag_isset(ups->status, ST_MASTER))
 		return 1;
@@ -743,6 +756,21 @@ static void upsreplbatt(utype_t *ups)
 	}
 }
 
+static void ups_cal(utype_t *ups)
+{
+	if (flag_isset(ups->status, ST_CAL)) { 	/* no change */
+		upsdebugx(4, "%s: %s (no change)", __func__, ups->sys);
+		return;
+	}
+
+	upsdebugx(3, "%s: %s (first time)", __func__, ups->sys);
+
+	/* must have changed from !CAL to CAL, so notify */
+
+	do_notify(ups, NOTIFY_CAL);
+	setflag(&ups->status, ST_CAL);
+}
+
 static void ups_fsd(utype_t *ups)
 {
 	if (flag_isset(ups->status, ST_FSD)) {		/* no change */
@@ -1372,9 +1400,10 @@ static void setup_signals(void)
 /* remember the last time the ups was not critical (OB + LB) */
 static void update_crittimer(utype_t *ups)
 {
-	/* if !OB or !LB, then it's not critical, so log the time */
-	if ((!flag_isset(ups->status, ST_ONBATT)) || 
-		(!flag_isset(ups->status, ST_LOWBATT))) {
+	/* if !OB, !LB, or CAL, then it's not critical, so log the time */
+	if ((!flag_isset(ups->status, ST_ONBATT))  || 
+		(!flag_isset(ups->status, ST_LOWBATT)) ||
+		(flag_isset(ups->status, ST_CAL))) {
 
 		time(&ups->lastnoncrit);
 		return;
@@ -1492,6 +1521,8 @@ static void parse_status(utype_t *ups, char *status)
 			ups_low_batt(ups);
 		if (!strcasecmp(statword, "RB"))
 			upsreplbatt(ups);
+		if (!strcasecmp(statword, "CAL"))
+			ups_cal(ups);
 
 		/* do it last to override any possible OL */
 		if (!strcasecmp(statword, "FSD"))
diff --git a/clients/upsmon.h b/clients/upsmon.h
index 2504370cf1..7fe98eb827 100644
--- a/clients/upsmon.h
+++ b/clients/upsmon.h
@@ -26,6 +26,7 @@
 #define ST_MASTER      (1 << 4)       /* we are the master on this UPS        */
 #define ST_LOGIN       (1 << 5)       /* we are logged into this UPS          */
 #define ST_CONNECTED   (1 << 6)       /* upscli_connect returned OK           */
+#define ST_CAL         (1 << 7)       /* UPS calibration in progress (CAL)    */
 
 /* required contents of flag file */
 #define SDMAGIC "upsmon-shutdown-file"  
@@ -75,6 +76,7 @@ typedef struct {
 #define NOTIFY_REPLBATT	7	/* UPS battery needs to be replaced	*/
 #define NOTIFY_NOCOMM	8	/* UPS hasn't been contacted in awhile	*/
 #define NOTIFY_NOPARENT	9	/* privileged parent process died	*/
+#define NOTIFY_CAL		10	/* UPS is performing calibration   */
 
 /* notify flag values */
 
@@ -104,6 +106,7 @@ struct {
 	{ NOTIFY_REPLBATT, "REPLBATT", NULL, "UPS %s battery needs to be replaced", NOTIFY_SYSLOG | NOTIFY_WALL },
 	{ NOTIFY_NOCOMM,   "NOCOMM",   NULL, "UPS %s is unavailable", NOTIFY_SYSLOG | NOTIFY_WALL },
 	{ NOTIFY_NOPARENT, "NOPARENT", NULL, "upsmon parent process died - shutdown impossible", NOTIFY_SYSLOG | NOTIFY_WALL },
+	{ NOTIFY_CAL,      "CAL",      NULL, "UPS %s: calibration in progress", NOTIFY_SYSLOG },
 	{ 0, NULL, NULL, NULL, 0 }
 };