diff --git a/src/main/fc/core.c b/src/main/fc/core.c
index 00c0a98b50..87e34e9d4b 100644
--- a/src/main/fc/core.c
+++ b/src/main/fc/core.c
@@ -130,7 +130,7 @@ int16_t magHold;
 
 static bool flipOverAfterCrashMode = false;
 
-static uint32_t disarmAt;     // Time of automatic disarm when "Don't spin the motors when armed" is enabled and auto_disarm_delay is nonzero
+static timeUs_t disarmAt;     // Time of automatic disarm when "Don't spin the motors when armed" is enabled and auto_disarm_delay is nonzero
 
 bool isRXDataNew;
 static int lastArmingDisabledReason = 0;
@@ -338,8 +338,11 @@ void tryArm(void)
         if (ARMING_FLAG(ARMED)) {
             return;
         }
+
+        const timeUs_t currentTimeUs = micros();
+
 #ifdef USE_DSHOT
-        if (micros() - getLastDshotBeaconCommandTimeUs() < DSHOT_BEACON_GUARD_DELAY_US) {
+        if (currentTimeUs - getLastDshotBeaconCommandTimeUs() < DSHOT_BEACON_GUARD_DELAY_US) {
             if (tryingToArm == ARMING_DELAYED_DISARMED) {
                 if (isModeActivationConditionPresent(BOXFLIPOVERAFTERCRASH) && IS_RC_MODE_ACTIVE(BOXFLIPOVERAFTERCRASH)) {
                     tryingToArm = ARMING_DELAYED_CRASHFLIP;
@@ -381,7 +384,7 @@ void tryArm(void)
         }
         imuQuaternionHeadfreeOffsetSet();
 
-        disarmAt = millis() + armingConfig()->auto_disarm_delay * 1000;   // start disarm timeout, will be extended when throttle is nonzero
+        disarmAt = currentTimeUs + armingConfig()->auto_disarm_delay * 1e6;   // start disarm timeout, will be extended when throttle is nonzero
 
         lastArmingDisabledReason = 0;
 
@@ -666,6 +669,7 @@ bool processRx(timeUs_t currentTimeUs)
     // When armed and motors aren't spinning, do beeps and then disarm
     // board after delay so users without buzzer won't lose fingers.
     // mixTable constrains motor commands, so checking  throttleStatus is enough
+    const timeUs_t autoDisarmDelayUs = armingConfig()->auto_disarm_delay * 1e6;
     if (ARMING_FLAG(ARMED)
         && featureIsEnabled(FEATURE_MOTOR_STOP)
         && !STATE(FIXED_WING)
@@ -674,9 +678,7 @@ bool processRx(timeUs_t currentTimeUs)
     ) {
         if (isUsingSticksForArming()) {
             if (throttleStatus == THROTTLE_LOW) {
-                if (armingConfig()->auto_disarm_delay != 0
-                    && (int32_t)(disarmAt - millis()) < 0
-                ) {
+                if ((autoDisarmDelayUs > 0) && (currentTimeUs > disarmAt)) {
                     // auto-disarm configured and delay is over
                     disarm();
                     armedBeeperOn = false;
@@ -686,11 +688,8 @@ bool processRx(timeUs_t currentTimeUs)
                     armedBeeperOn = true;
                 }
             } else {
-                // throttle is not low
-                if (armingConfig()->auto_disarm_delay != 0) {
-                    // extend disarm time
-                    disarmAt = millis() + armingConfig()->auto_disarm_delay * 1000;
-                }
+                // throttle is not low - extend disarm time
+                disarmAt = currentTimeUs + autoDisarmDelayUs;
 
                 if (armedBeeperOn) {
                     beeperSilence();
@@ -707,6 +706,8 @@ bool processRx(timeUs_t currentTimeUs)
                 armedBeeperOn = false;
             }
         }
+    } else {
+        disarmAt = currentTimeUs + autoDisarmDelayUs;  // extend auto-disarm timer
     }
 
     processRcStickPositions();