diff --git a/accessible/ipc/RemoteAccessibleBase.cpp b/accessible/ipc/RemoteAccessibleBase.cpp
index eedd0cffa197..acf73a1481c8 100644
--- a/accessible/ipc/RemoteAccessibleBase.cpp
+++ b/accessible/ipc/RemoteAccessibleBase.cpp
@@ -630,6 +630,22 @@ LayoutDeviceIntRect RemoteAccessibleBase<Derived>::Bounds() const {
 template <class Derived>
 Relation RemoteAccessibleBase<Derived>::RelationByType(
     RelationType aType) const {
+  // We are able to handle some relations completely in the
+  // parent process, without the help of the cache. Those
+  // relations are enumerated here. Other relations, whose
+  // types are stored in kRelationTypeAtoms, are processed
+  // below using the cache.
+  if (aType == RelationType::CONTAINING_TAB_PANE) {
+    if (dom::CanonicalBrowsingContext* cbc = mDoc->GetBrowsingContext()) {
+      if (dom::CanonicalBrowsingContext* topCbc = cbc->Top()) {
+        if (dom::BrowserParent* bp = topCbc->GetBrowserParent()) {
+          return Relation(bp->GetTopLevelDocAccessible());
+        }
+      }
+    }
+    return Relation();
+  }
+
   Relation rel;
   if (!mCachedFields) {
     return rel;
diff --git a/accessible/tests/browser/e10s/browser_caching_relations.js b/accessible/tests/browser/e10s/browser_caching_relations.js
index b3a50737712b..598e48a18d95 100644
--- a/accessible/tests/browser/e10s/browser_caching_relations.js
+++ b/accessible/tests/browser/e10s/browser_caching_relations.js
@@ -322,3 +322,33 @@ addAccessibleTask(
   },
   { chrome: true, iframe: true, remoteIframe: true }
 );
+
+/**
+ * Test CONTAINING_TAB_PANE
+ */
+addAccessibleTask(
+  `<p id="p">hello world</p>`,
+  async function(browser, primaryDocAcc, secondaryDocAcc) {
+    // The CONTAINING_TAB_PANE of any acc should be the top level
+    // content document. If this test runs in an iframe,
+    // the test harness will pass in doc accs for both the
+    // iframe (primaryDocAcc) and the top level remote
+    // browser (secondaryDocAcc). We should use the second
+    // one.
+    // If this is not in an iframe, we'll only get
+    // a single docAcc (primaryDocAcc) which refers to
+    // the top level content doc.
+    const topLevelDoc = secondaryDocAcc ? secondaryDocAcc : primaryDocAcc;
+    await testCachedRelation(
+      findAccessibleChildByID(primaryDocAcc, "p"),
+      RELATION_CONTAINING_TAB_PANE,
+      topLevelDoc
+    );
+  },
+  {
+    chrome: true,
+    topLevel: isCacheEnabled,
+    iframe: isCacheEnabled,
+    remoteIframe: isCacheEnabled,
+  }
+);
diff --git a/accessible/windows/msaa/MsaaAccessible.cpp b/accessible/windows/msaa/MsaaAccessible.cpp
index 02565e40e820..914c39513d93 100644
--- a/accessible/windows/msaa/MsaaAccessible.cpp
+++ b/accessible/windows/msaa/MsaaAccessible.cpp
@@ -795,6 +795,10 @@ ITypeInfo* MsaaAccessible::GetTI(LCID lcid) {
 
 /* static */
 MsaaAccessible* MsaaAccessible::GetFrom(Accessible* aAcc) {
+  if (!aAcc) {
+    return nullptr;
+  }
+
   if (RemoteAccessible* remoteAcc = aAcc->AsRemote()) {
     return reinterpret_cast<MsaaAccessible*>(remoteAcc->GetWrapper());
   }
diff --git a/accessible/windows/msaa/ServiceProvider.cpp b/accessible/windows/msaa/ServiceProvider.cpp
index decc5c5d3e9c..98542a230cf5 100644
--- a/accessible/windows/msaa/ServiceProvider.cpp
+++ b/accessible/windows/msaa/ServiceProvider.cpp
@@ -17,6 +17,7 @@
 
 #include "mozilla/a11y/DocAccessibleChild.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_accessibility.h"
 
 #include "ISimpleDOM.h"
 
@@ -62,7 +63,7 @@ ServiceProvider::QueryService(REFGUID aGuidService, REFIID aIID,
       0x3571,
       0x4d8f,
       {0x95, 0x21, 0x07, 0xed, 0x28, 0xfb, 0x07, 0x2e}};
-  if (aGuidService == SID_IAccessibleContentDocument && localAcc) {
+  if (aGuidService == SID_IAccessibleContentDocument) {
     if (aIID != IID_IAccessible) return E_NOINTERFACE;
 
     // If acc is within an OOP iframe document, the top level document
@@ -83,13 +84,16 @@ ServiceProvider::QueryService(REFGUID aGuidService, REFIID aIID,
       }
     }
 
-    Relation rel = localAcc->RelationByType(RelationType::CONTAINING_TAB_PANE);
-    AccessibleWrap* tabDoc = static_cast<AccessibleWrap*>(rel.LocalNext());
-    if (!tabDoc) return E_NOINTERFACE;
+    MOZ_ASSERT(
+        acc->IsLocal() || StaticPrefs::accessibility_cache_enabled_AtStartup(),
+        "We should only handle remote accs here if the cache is on!");
+    Relation rel = acc->RelationByType(RelationType::CONTAINING_TAB_PANE);
+    RefPtr<IAccessible> next = MsaaAccessible::GetFrom(rel.Next());
+    if (!next) {
+      return E_NOINTERFACE;
+    }
 
-    RefPtr<IAccessible> result;
-    tabDoc->GetNativeInterface(getter_AddRefs(result));
-    result.forget(aInstancePtr);
+    next.forget(aInstancePtr);
     return S_OK;
   }