diff --git a/toolkit/components/places/nsINavBookmarksService.idl b/toolkit/components/places/nsINavBookmarksService.idl
index 1c54d0231c6e..d1b38b94b205 100644
--- a/toolkit/components/places/nsINavBookmarksService.idl
+++ b/toolkit/components/places/nsINavBookmarksService.idl
@@ -456,6 +456,5 @@ interface nsINavBookmarksService : nsISupports
   /**
    * Gets an array of registered nsINavBookmarkObserver objects.
    */
-  void getObservers([optional] out unsigned long count,
-                    [retval, array, size_is(count)] out nsINavBookmarkObserver observers);
+  Array<nsINavBookmarkObserver> getObservers();
 };
diff --git a/toolkit/components/places/nsINavHistoryService.idl b/toolkit/components/places/nsINavHistoryService.idl
index 2835e40eceec..406f89472479 100644
--- a/toolkit/components/places/nsINavHistoryService.idl
+++ b/toolkit/components/places/nsINavHistoryService.idl
@@ -1261,8 +1261,7 @@ interface nsINavHistoryService : nsISupports
   /**
    * Gets an array of registered nsINavHistoryObserver objects.
    */
-  void getObservers([optional] out unsigned long count,
-                    [retval, array, size_is(count)] out nsINavHistoryObserver observers);
+  Array<nsINavHistoryObserver> getObservers();
 
   /**
    * True if history is disabled. currently,
diff --git a/toolkit/components/places/nsNavBookmarks.cpp b/toolkit/components/places/nsNavBookmarks.cpp
index 1e3f59959383..910cac6ba811 100644
--- a/toolkit/components/places/nsNavBookmarks.cpp
+++ b/toolkit/components/places/nsNavBookmarks.cpp
@@ -1763,30 +1763,20 @@ nsNavBookmarks::RemoveObserver(nsINavBookmarkObserver* aObserver) {
 }
 
 NS_IMETHODIMP
-nsNavBookmarks::GetObservers(uint32_t* _count,
-                             nsINavBookmarkObserver*** _observers) {
-  NS_ENSURE_ARG_POINTER(_count);
-  NS_ENSURE_ARG_POINTER(_observers);
-
-  *_count = 0;
-  *_observers = nullptr;
+nsNavBookmarks::GetObservers(nsTArray<RefPtr<nsINavBookmarkObserver>>& aObservers) {
+  aObservers.Clear();
 
   if (!mCanNotify) return NS_OK;
 
-  nsCOMArray<nsINavBookmarkObserver> observers;
-
   for (uint32_t i = 0; i < mObservers.Length(); ++i) {
-    const nsCOMPtr<nsINavBookmarkObserver>& observer =
+    nsCOMPtr<nsINavBookmarkObserver> observer =
         mObservers.ElementAt(i).GetValue();
     // Skip nullified weak observers.
-    if (observer) observers.AppendElement(observer);
+    if (observer) {
+      aObservers.AppendElement(observer.forget());
+    }
   }
 
-  if (observers.Count() == 0) return NS_OK;
-
-  *_count = observers.Count();
-  observers.Forget(_observers);
-
   return NS_OK;
 }
 
diff --git a/toolkit/components/places/nsNavHistory.cpp b/toolkit/components/places/nsNavHistory.cpp
index b7287a03b541..3037008f7417 100644
--- a/toolkit/components/places/nsNavHistory.cpp
+++ b/toolkit/components/places/nsNavHistory.cpp
@@ -2025,13 +2025,8 @@ nsNavHistory::RemoveObserver(nsINavHistoryObserver* aObserver) {
 }
 
 NS_IMETHODIMP
-nsNavHistory::GetObservers(uint32_t* _count,
-                           nsINavHistoryObserver*** _observers) {
-  NS_ENSURE_ARG_POINTER(_count);
-  NS_ENSURE_ARG_POINTER(_observers);
-
-  *_count = 0;
-  *_observers = nullptr;
+nsNavHistory::GetObservers(nsTArray<RefPtr<nsINavHistoryObserver>>& aObservers) {
+  aObservers.Clear();
 
   // Clear any cached value, cause it's very likely the consumer has made
   // changes to history and is now trying to notify them.
@@ -2039,21 +2034,16 @@ nsNavHistory::GetObservers(uint32_t* _count,
 
   if (!mCanNotify) return NS_OK;
 
-  nsCOMArray<nsINavHistoryObserver> observers;
-
   // Then add the other observers.
   for (uint32_t i = 0; i < mObservers.Length(); ++i) {
-    const nsCOMPtr<nsINavHistoryObserver>& observer =
+    nsCOMPtr<nsINavHistoryObserver> observer =
         mObservers.ElementAt(i).GetValue();
     // Skip nullified weak observers.
-    if (observer) observers.AppendElement(observer);
+    if (observer) {
+      aObservers.AppendElement(observer.forget());
+    }
   }
 
-  if (observers.Count() == 0) return NS_OK;
-
-  *_count = observers.Count();
-  observers.Forget(_observers);
-
   return NS_OK;
 }