diff --git a/lib/icinga/service-comment.cpp b/lib/icinga/service-comment.cpp
index 23c80af6c..0a02be8bd 100644
--- a/lib/icinga/service-comment.cpp
+++ b/lib/icinga/service-comment.cpp
@@ -82,9 +82,13 @@ String Service::AddComment(CommentType entryType, const String& author,
 	}
 
 	String id = Utility::NewUniqueID();
-	comments->Set(id, comment);
 
-	Touch("comments");
+	{
+		ObjectLock olock(this);
+
+		comments->Set(id, comment);
+		Touch("comments");
+	}
 
 	return id;
 }
@@ -105,6 +109,8 @@ void Service::RemoveComment(const String& id)
 	Dictionary::Ptr comments = owner->GetComments();
 
 	if (comments) {
+		ObjectLock olock(owner);
+
 		comments->Remove(id);
 		owner->Touch("comments");
 	}
@@ -208,7 +214,11 @@ void Service::RefreshCommentsCache(void)
 
 				legacy_id = l_NextCommentID++;
 				comment->Set("legacy_id", legacy_id);
-				service->Touch("comments");
+
+				{
+					ObjectLock olock(service);
+					service->Touch("comments");
+				}
 			}
 
 			newLegacyCommentsCache[legacy_id] = id;
@@ -254,6 +264,7 @@ void Service::RemoveExpiredComments(void)
 			comments->Remove(id);
 		}
 
+		ObjectLock olock(this);
 		Touch("comments");
 	}
 }
diff --git a/lib/icinga/service-downtime.cpp b/lib/icinga/service-downtime.cpp
index 654e3f46f..5720e35c6 100644
--- a/lib/icinga/service-downtime.cpp
+++ b/lib/icinga/service-downtime.cpp
@@ -79,8 +79,12 @@ String Service::AddDowntime(const String& author, const String& comment,
 		Dictionary::Ptr otherDowntimes = otherOwner->Get("downtimes");
 		Dictionary::Ptr otherDowntime = otherDowntimes->Get(triggeredBy);
 		Dictionary::Ptr triggers = otherDowntime->Get("triggers");
-		triggers->Set(triggeredBy, triggeredBy);
-		otherOwner->Touch("downtimes");
+
+		{
+			ObjectLock olock(otherOwner);
+			triggers->Set(triggeredBy, triggeredBy);
+			otherOwner->Touch("downtimes");
+		}
 	}
 
 	Dictionary::Ptr downtimes;
@@ -99,7 +103,12 @@ String Service::AddDowntime(const String& author, const String& comment,
 	String id = Utility::NewUniqueID();
 	downtimes->Set(id, downtime);
 
-	Touch("downtimes");
+	{
+		ObjectLock olock(this);
+		Touch("downtimes");
+	}
+
+	(void) AddComment(CommentDowntime, author, comment, endTime);
 
 	return id;
 }
@@ -116,8 +125,11 @@ void Service::RemoveDowntime(const String& id)
 	if (!downtimes)
 		return;
 
-	downtimes->Remove(id);
-	owner->Touch("downtimes");
+	{
+		ObjectLock olock(owner);
+		downtimes->Remove(id);
+		owner->Touch("downtimes");
+	}
 }
 
 void Service::TriggerDowntimes(void)