diff --git a/plugins/github/src/org/jetbrains/plugins/github/api/data/pullrequest/timeline/GHPRTimelineItem.kt b/plugins/github/src/org/jetbrains/plugins/github/api/data/pullrequest/timeline/GHPRTimelineItem.kt
index 10e5c60e8593..bfbb8f0cbbca 100644
--- a/plugins/github/src/org/jetbrains/plugins/github/api/data/pullrequest/timeline/GHPRTimelineItem.kt
+++ b/plugins/github/src/org/jetbrains/plugins/github/api/data/pullrequest/timeline/GHPRTimelineItem.kt
@@ -1,4 +1,4 @@
-// Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.plugins.github.api.data.pullrequest.timeline
 
 import com.fasterxml.jackson.annotation.JsonSubTypes
@@ -47,7 +47,7 @@ SubscribedEvent | UnsubscribedEvent
 MilestonedEvent | DemilestonedEvent
 MentionedEvent | ReferencedEvent | CrossReferencedEvent
  */
-@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "__typename", visible = false,
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "__typename", visible = true,
               defaultImpl = Unknown::class)
 @JsonSubTypes(
   JsonSubTypes.Type(name = "IssueComment", value = GHIssueComment::class),
@@ -79,5 +79,5 @@ MentionedEvent | ReferencedEvent | CrossReferencedEvent
   JsonSubTypes.Type(name = "HeadRefRestoredEvent", value = GHPRHeadRefRestoredEvent::class)
 )
 interface GHPRTimelineItem {
-  class Unknown : GHPRTimelineItem
+  class Unknown(val __typename: String) : GHPRTimelineItem
 }
\ No newline at end of file
diff --git a/plugins/github/src/org/jetbrains/plugins/github/pullrequest/ui/timeline/GHPRTimelineItemComponentFactory.kt b/plugins/github/src/org/jetbrains/plugins/github/pullrequest/ui/timeline/GHPRTimelineItemComponentFactory.kt
index f2ee438f9919..80171ad8e041 100644
--- a/plugins/github/src/org/jetbrains/plugins/github/pullrequest/ui/timeline/GHPRTimelineItemComponentFactory.kt
+++ b/plugins/github/src/org/jetbrains/plugins/github/pullrequest/ui/timeline/GHPRTimelineItemComponentFactory.kt
@@ -49,7 +49,8 @@ class GHPRTimelineItemComponentFactory(private val reviewDataProvider: GHPRRevie
         is GHPullRequestReview -> createComponent(item)
 
         is GHPRTimelineEvent -> eventComponentFactory.createComponent(item)
-        else -> throw IllegalStateException("Unknown item type")
+        is GHPRTimelineItem.Unknown -> throw IllegalStateException("Unknown item type: " + item.__typename)
+        else -> error("Undefined item type")
       }
     }
     catch (e: Exception) {