diff --git a/changelog.d/5886.bugfix b/changelog.d/5886.bugfix
new file mode 100644
index 0000000000..c4239e5c3a
--- /dev/null
+++ b/changelog.d/5886.bugfix
@@ -0,0 +1 @@
+Fix UISIDetector grace period bug
diff --git a/vector/src/main/java/im/vector/app/UISIDetector.kt b/vector/src/main/java/im/vector/app/UISIDetector.kt
index fea1861cc6..4a9d8ae266 100644
--- a/vector/src/main/java/im/vector/app/UISIDetector.kt
+++ b/vector/src/main/java/im/vector/app/UISIDetector.kt
@@ -52,7 +52,7 @@ data class E2EMessageDetected(
     }
 }
 
-class UISIDetector : LiveEventListener {
+class UISIDetector(private val timeoutMillis: Long = 30_000L) : LiveEventListener {
 
     interface UISIDetectorCallback {
         val enabled: Boolean
@@ -66,7 +66,6 @@ class UISIDetector : LiveEventListener {
     private val trackedEvents = mutableMapOf<String, TimerTask>()
     private val executor = Executors.newSingleThreadExecutor()
     private val timer = Timer()
-    private val timeoutMillis = 30_000L
     private val enabled: Boolean get() = callback?.enabled.orFalse()
 
     override fun onEventDecrypted(event: Event, clearEvent: JsonDict) {
@@ -90,22 +89,27 @@ class UISIDetector : LiveEventListener {
         val roomId = event.roomId
         if (!enabled || eventId == null || roomId == null) return
 
-        val trackerId: String = trackerId(eventId, roomId)
-        if (trackedEvents.containsKey(trackerId)) {
-            Timber.w("## UISIDetector: Event $eventId is already tracked")
+        val trackedId: String = trackedId(eventId, roomId)
+        if (trackedEvents.containsKey(trackedId)) {
+            Timber.v("## UISIDetector: Event $eventId is already tracked")
             return
         }
         // track it and start timer
         val timeoutTask = object : TimerTask() {
             override fun run() {
                 executor.execute {
+                    // we should check if it's still tracked (it might have been decrypted)
+                    if (!trackedEvents.containsKey(trackedId)) {
+                        Timber.v("## UISIDetector: E2E error for $eventId was resolved")
+                        return@execute
+                    }
                     unTrack(eventId, roomId)
                     Timber.v("## UISIDetector: Timeout on $eventId")
                     triggerUISI(E2EMessageDetected.fromEvent(event, roomId))
                 }
             }
         }
-        trackedEvents[trackerId] = timeoutTask
+        trackedEvents[trackedId] = timeoutTask
         timer.schedule(timeoutTask, timeoutMillis)
     }
 
@@ -113,7 +117,7 @@ class UISIDetector : LiveEventListener {
 
     override fun onPaginatedEvent(roomId: String, event: Event) {}
 
-    private fun trackerId(eventId: String, roomId: String): String = "$roomId-$eventId"
+    private fun trackedId(eventId: String, roomId: String): String = "$roomId-$eventId"
 
     private fun triggerUISI(source: E2EMessageDetected) {
         if (!enabled) return
@@ -122,6 +126,6 @@ class UISIDetector : LiveEventListener {
     }
 
     private fun unTrack(eventId: String, roomId: String) {
-        trackedEvents.remove(trackerId(eventId, roomId))?.cancel()
+        trackedEvents.remove(trackedId(eventId, roomId))?.cancel()
     }
 }
diff --git a/vector/src/test/java/im/vector/app/features/crypto/UISIDetectorTest.kt b/vector/src/test/java/im/vector/app/features/crypto/UISIDetectorTest.kt
new file mode 100644
index 0000000000..d47855d75e
--- /dev/null
+++ b/vector/src/test/java/im/vector/app/features/crypto/UISIDetectorTest.kt
@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2022 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package im.vector.app.features.crypto
+
+import im.vector.app.E2EMessageDetected
+import im.vector.app.UISIDetector
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+import org.amshove.kluent.fail
+import org.junit.Assert
+import org.junit.Test
+import org.matrix.android.sdk.api.crypto.MXCRYPTO_ALGORITHM_MEGOLM
+import org.matrix.android.sdk.api.session.crypto.MXCryptoError
+import org.matrix.android.sdk.api.session.events.model.Event
+import org.matrix.android.sdk.api.session.events.model.EventType
+import org.matrix.android.sdk.api.session.events.model.content.EncryptedEventContent
+import org.matrix.android.sdk.api.session.events.model.toContent
+
+class UISIDetectorTest {
+
+    @Test
+    fun `trigger detection after grace period`() {
+        val gracePeriod = 5_000L
+        val uisiDetector = UISIDetector(gracePeriod)
+        var detectedEvent: E2EMessageDetected? = null
+
+        uisiDetector.callback = object : UISIDetector.UISIDetectorCallback {
+            override val enabled = true
+            override val reciprocateToDeviceEventType = "foo"
+
+            override fun uisiDetected(source: E2EMessageDetected) {
+                detectedEvent = source
+            }
+
+            override fun uisiReciprocateRequest(source: Event) {
+                // nop
+            }
+        }
+
+        // report a decryption error
+        val eventId = "0001"
+        val event = fakeEncryptedEvent(eventId, "s1", "r1")
+        uisiDetector.onEventDecryptionError(event, fakeCryptoError())
+
+        runBlocking {
+            delay((gracePeriod * 1.2).toLong())
+        }
+        Assert.assertEquals(eventId, detectedEvent?.eventId)
+    }
+
+    @Test
+    fun `If event decrypted during grace period should not trigger detection`() {
+        val scope = CoroutineScope(SupervisorJob())
+        val gracePeriod = 5_000L
+        val uisiDetector = UISIDetector(gracePeriod)
+
+        uisiDetector.callback = object : UISIDetector.UISIDetectorCallback {
+            override val enabled = true
+            override val reciprocateToDeviceEventType = "foo"
+
+            override fun uisiDetected(source: E2EMessageDetected) {
+                fail("Shouldn't trigger")
+            }
+
+            override fun uisiReciprocateRequest(source: Event) {
+                // nop
+            }
+        }
+
+        // report a decryption error
+        val event = fakeEncryptedEvent("0001", "s1", "r1")
+        uisiDetector.onEventDecryptionError(event, fakeCryptoError())
+
+        // the grace period is 30s
+        scope.launch(Dispatchers.Default) {
+            delay((gracePeriod * 0.5).toLong())
+            uisiDetector.onEventDecrypted(event, emptyMap())
+        }
+
+        runBlocking {
+            delay((gracePeriod * 1.2).toLong())
+        }
+    }
+
+    private fun fakeEncryptedEvent(eventId: String, sessionId: String, roomId: String): Event {
+        return Event(
+                type = EventType.ENCRYPTED,
+                eventId = eventId,
+                roomId = roomId,
+                content = EncryptedEventContent(
+                        algorithm = MXCRYPTO_ALGORITHM_MEGOLM,
+                        ciphertext = "AwgBEpACQEKOkd4Gp0+gSXG4M+btcrnPgsF23xs/lUmS2I4YjmqF...",
+                        sessionId = sessionId,
+                        senderKey = "5e3EIqg3JfooZnLQ2qHIcBarbassQ4qXblai0",
+                        deviceId = "FAKEE"
+                ).toContent()
+        )
+    }
+
+    private fun fakeCryptoError(error: MXCryptoError.ErrorType = MXCryptoError.ErrorType.UNKNOWN_INBOUND_SESSION_ID) = MXCryptoError.Base(
+            error,
+            "A description",
+            "Human readable"
+    )
+}