diff --git a/layout/base/AccessibleCaretEventHub.cpp b/layout/base/AccessibleCaretEventHub.cpp
index 4dbd1556d27..4105064a482 100644
--- a/layout/base/AccessibleCaretEventHub.cpp
+++ b/layout/base/AccessibleCaretEventHub.cpp
@@ -473,6 +473,8 @@ AccessibleCaretEventHub::HandleEvent(WidgetEvent* aEvent)
     return status;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   switch (aEvent->mClass) {
   case eMouseEventClass:
     status = HandleMouseEvent(aEvent->AsMouseEvent());
@@ -655,6 +657,8 @@ AccessibleCaretEventHub::Reflow(DOMHighResTimeStamp aStart,
     return NS_OK;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   AC_LOG("%s, state: %s", __FUNCTION__, mState->Name());
   mState->OnReflow(this);
   return NS_OK;
@@ -668,6 +672,8 @@ AccessibleCaretEventHub::ReflowInterruptible(DOMHighResTimeStamp aStart,
     return NS_OK;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   return Reflow(aStart, aEnd);
 }
 
@@ -678,6 +684,8 @@ AccessibleCaretEventHub::AsyncPanZoomStarted()
     return;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   AC_LOG("%s, state: %s", __FUNCTION__, mState->Name());
   mState->OnScrollStart(this);
 }
@@ -689,6 +697,8 @@ AccessibleCaretEventHub::AsyncPanZoomStopped()
     return;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   AC_LOG("%s, state: %s", __FUNCTION__, mState->Name());
   mState->OnScrollEnd(this);
 }
@@ -700,6 +710,8 @@ AccessibleCaretEventHub::ScrollPositionChanged()
     return;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   AC_LOG("%s, state: %s", __FUNCTION__, mState->Name());
   mState->OnScrollPositionChanged(this);
 }
@@ -742,6 +754,8 @@ AccessibleCaretEventHub::NotifySelectionChanged(nsIDOMDocument* aDoc,
     return NS_OK;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   AC_LOG("%s, state: %s, reason: %d", __FUNCTION__, mState->Name(), aReason);
   mState->OnSelectionChanged(this, aDoc, aSel, aReason);
   return NS_OK;
@@ -754,6 +768,8 @@ AccessibleCaretEventHub::NotifyBlur(bool aIsLeavingDocument)
     return;
   }
 
+  MOZ_ASSERT(mRefCnt.get() > 1, "Expect caller holds us as well!");
+
   AC_LOG("%s, state: %s", __FUNCTION__, mState->Name());
   mState->OnBlur(this, aIsLeavingDocument);
 }
diff --git a/layout/base/gtest/TestAccessibleCaretEventHub.cpp b/layout/base/gtest/TestAccessibleCaretEventHub.cpp
index 50215901aa2..2f230c48fda 100644
--- a/layout/base/gtest/TestAccessibleCaretEventHub.cpp
+++ b/layout/base/gtest/TestAccessibleCaretEventHub.cpp
@@ -35,7 +35,7 @@ namespace mozilla
 class MockAccessibleCaretManager : public AccessibleCaretManager
 {
 public:
-  explicit MockAccessibleCaretManager()
+  MockAccessibleCaretManager()
     : AccessibleCaretManager(nullptr)
   {
   }
@@ -63,7 +63,7 @@ public:
   using AccessibleCaretEventHub::LongTapState;
   using AccessibleCaretEventHub::FireScrollEnd;
 
-  explicit MockAccessibleCaretEventHub()
+  MockAccessibleCaretEventHub()
     : AccessibleCaretEventHub(nullptr)
   {
     mManager = MakeUnique<MockAccessibleCaretManager>();
@@ -101,10 +101,20 @@ public:
 class AccessibleCaretEventHubTester : public ::testing::Test
 {
 public:
-  explicit AccessibleCaretEventHubTester()
+  AccessibleCaretEventHubTester()
   {
     DefaultValue<nsresult>::Set(NS_OK);
     EXPECT_EQ(mHub->GetState(), MockAccessibleCaretEventHub::NoActionState());
+
+    // AccessibleCaretEventHub requires the caller to hold a ref to it. We just
+    // add ref here for the sake of convenience.
+    mHub.get()->AddRef();
+  }
+
+  ~AccessibleCaretEventHubTester()
+  {
+    // Release the ref added in the constructor.
+    mHub.get()->Release();
   }
 
   static UniquePtr<WidgetEvent> CreateMouseEvent(EventMessage aMessage,