diff --git a/xpcom/base/nsMaybeWeakPtr.h b/xpcom/base/nsMaybeWeakPtr.h
index c2d0376259d5..165a8c23c182 100644
--- a/xpcom/base/nsMaybeWeakPtr.h
+++ b/xpcom/base/nsMaybeWeakPtr.h
@@ -54,7 +54,7 @@ class nsMaybeWeakPtr {
 // given object to appear in the array once.
 
 template <class T>
-class nsMaybeWeakPtrArray : public nsTArray<nsMaybeWeakPtr<T>> {
+class nsMaybeWeakPtrArray : public CopyableTArray<nsMaybeWeakPtr<T>> {
   typedef nsTArray<nsMaybeWeakPtr<T>> MaybeWeakArray;
 
   nsresult SetMaybeWeakPtr(nsMaybeWeakPtr<T>& aRef, T* aElement,
diff --git a/xpcom/ds/nsTObserverArray.h b/xpcom/ds/nsTObserverArray.h
index 89d4e7406c7b..9b488704d2b7 100644
--- a/xpcom/ds/nsTObserverArray.h
+++ b/xpcom/ds/nsTObserverArray.h
@@ -410,6 +410,12 @@ class nsTObserverArray : public nsAutoTObserverArray<T, 0> {
   explicit nsTObserverArray(size_type aCapacity) {
     base_type::mArray.SetCapacity(aCapacity);
   }
+
+  nsTObserverArray Clone() const {
+    auto result = nsTObserverArray{};
+    result.mArray.Assign(this->mArray);
+    return result;
+  }
 };
 
 template <typename T, size_t N>
diff --git a/xpcom/ds/nsTPriorityQueue.h b/xpcom/ds/nsTPriorityQueue.h
index c3397365a0db..b5a02957c018 100644
--- a/xpcom/ds/nsTPriorityQueue.h
+++ b/xpcom/ds/nsTPriorityQueue.h
@@ -146,7 +146,7 @@ class nsTPriorityQueue {
     mElements[aIndexB] = temp;
   }
 
-  nsTArray<T> mElements;
+  CopyableTArray<T> mElements;
   Compare mCompare;  // Comparator object
 };
 
diff --git a/xpcom/io/nsPipe3.cpp b/xpcom/io/nsPipe3.cpp
index 9c0ab794e9d0..93b102457bdd 100644
--- a/xpcom/io/nsPipe3.cpp
+++ b/xpcom/io/nsPipe3.cpp
@@ -939,7 +939,7 @@ void nsPipe::OnPipeException(nsresult aReason, bool aOutputOnly) {
 
     // OnInputException() can drain the stream and remove it from
     // mInputList.  So iterate over a temp list instead.
-    nsTArray<nsPipeInputStream*> list(mInputList);
+    nsTArray<nsPipeInputStream*> list = mInputList.Clone();
     for (uint32_t i = 0; i < list.Length(); ++i) {
       // an output-only exception applies to the input end if the pipe has
       // zero bytes available.
diff --git a/xpcom/tests/gtest/TestTArray.cpp b/xpcom/tests/gtest/TestTArray.cpp
index bed33bbc40fa..30655dc01afc 100644
--- a/xpcom/tests/gtest/TestTArray.cpp
+++ b/xpcom/tests/gtest/TestTArray.cpp
@@ -119,7 +119,7 @@ TEST(TArray, int_AppendElements_TArray_Copy)
 {
   nsTArray<int> array;
 
-  const nsTArray<int> temp(DummyArray());
+  const nsTArray<int> temp(DummyArray().Clone());
   int* ptr = array.AppendElements(temp);
   ASSERT_EQ(&array[0], ptr);
   ASSERT_EQ(DummyArray(), array);
@@ -138,7 +138,7 @@ TEST(TArray, int_AppendElements_TArray_Copy_Fallible)
 {
   nsTArray<int> array;
 
-  const nsTArray<int> temp(DummyArray());
+  const nsTArray<int> temp(DummyArray().Clone());
   int* ptr = array.AppendElements(temp, fallible);
   ASSERT_EQ(&array[0], ptr);
   ASSERT_EQ(DummyArray(), array);
@@ -157,13 +157,13 @@ TEST(TArray, int_AppendElements_TArray_Rvalue)
 {
   nsTArray<int> array;
 
-  nsTArray<int> temp(DummyArray());
+  nsTArray<int> temp(DummyArray().Clone());
   int* ptr = array.AppendElements(std::move(temp));
   ASSERT_EQ(&array[0], ptr);
   ASSERT_EQ(DummyArray(), array);
   ASSERT_TRUE(temp.IsEmpty());
 
-  temp = DummyArray();
+  temp = DummyArray().Clone();
   ptr = array.AppendElements(std::move(temp));
   ASSERT_EQ(&array[DummyArray().Length()], ptr);
   nsTArray<int> expected;
@@ -177,13 +177,13 @@ TEST(TArray, int_AppendElements_TArray_Rvalue_Fallible)
 {
   nsTArray<int> array;
 
-  nsTArray<int> temp(DummyArray());
+  nsTArray<int> temp(DummyArray().Clone());
   int* ptr = array.AppendElements(std::move(temp), fallible);
   ASSERT_EQ(&array[0], ptr);
   ASSERT_EQ(DummyArray(), array);
   ASSERT_TRUE(temp.IsEmpty());
 
-  temp = DummyArray();
+  temp = DummyArray().Clone();
   ptr = array.AppendElements(std::move(temp), fallible);
   ASSERT_EQ(&array[DummyArray().Length()], ptr);
   nsTArray<int> expected;
@@ -239,7 +239,7 @@ TEST(TArray, AppendElementsSpan)
 {
   nsTArray<int> array;
 
-  nsTArray<int> temp(DummyArray());
+  nsTArray<int> temp(DummyArray().Clone());
   Span<int> span = temp;
   array.AppendElements(span);
   ASSERT_EQ(DummyArray(), array);
@@ -489,7 +489,7 @@ TEST(TArray, int_Assign)
 
 TEST(TArray, int_AssignmentOperatorSelfAssignment)
 {
-  nsTArray<int> array;
+  CopyableTArray<int> array;
   array = DummyArray();
 
   array = *&array;
diff --git a/xpcom/tests/gtest/TestTArray2.cpp b/xpcom/tests/gtest/TestTArray2.cpp
index 82a647f40a77..139f2d66c419 100644
--- a/xpcom/tests/gtest/TestTArray2.cpp
+++ b/xpcom/tests/gtest/TestTArray2.cpp
@@ -35,7 +35,7 @@ inline bool operator<(const nsCOMPtr<T>& lhs, const nsCOMPtr<T>& rhs) {
 template <class ElementType>
 static bool test_basic_array(ElementType* data, size_t dataLen,
                              const ElementType& extra) {
-  nsTArray<ElementType> ary;
+  CopyableTArray<ElementType> ary;
   const nsTArray<ElementType>& cary = ary;
 
   ary.AppendElements(data, dataLen);
@@ -143,7 +143,7 @@ static bool test_basic_array(ElementType* data, size_t dataLen,
           []() { return false; }))
     return false;
 
-  nsTArray<ElementType> copy(ary);
+  nsTArray<ElementType> copy(ary.Clone());
   if (!(ary == copy)) return false;
   for (i = 0; i < copy.Length(); ++i) {
     if (ary[i] != copy[i]) return false;
@@ -380,7 +380,7 @@ TEST(TArray, test_move_array)
 
   ASSERT_EQ(Countable::Count(), 8);
 
-  nsTArray<Countable> copyCountableArray(constRefCountableArray);
+  nsTArray<Countable> copyCountableArray(constRefCountableArray.Clone());
 
   ASSERT_EQ(Countable::Count(), 12);
 
@@ -426,7 +426,7 @@ TEST(TArray, test_move_array)
 
   ASSERT_EQ(Moveable::Count(), 4);
 
-  nsTArray<Moveable> copyMoveableArray(constRefMoveableArray);
+  nsTArray<Moveable> copyMoveableArray(constRefMoveableArray.Clone());
 
   ASSERT_EQ(Moveable::Count(), 8);