diff --git a/mfbt/TypeTraits.h b/mfbt/TypeTraits.h
index 681edaa1fe2b..2e9a8821e4aa 100644
--- a/mfbt/TypeTraits.h
+++ b/mfbt/TypeTraits.h
@@ -288,19 +288,6 @@ template <typename T>
 struct IsMemberPointer
     : detail::IsMemberPointerHelper<typename RemoveCV<T>::Type> {};
 
-/**
- * IsScalar determines whether a type is a scalar type.
- *
- * mozilla::IsScalar<int>::value is true
- * mozilla::IsScalar<int*>::value is true
- * mozilla::IsScalar<cls>::value is false
- */
-template <typename T>
-struct IsScalar
-    : IntegralConstant<bool, IsArithmetic<T>::value || IsEnum<T>::value ||
-                                 IsPointer<T>::value ||
-                                 IsMemberPointer<T>::value> {};
-
 /* 20.9.4.3 Type properties [meta.unary.prop] */
 
 /**
diff --git a/mfbt/tests/TestTypeTraits.cpp b/mfbt/tests/TestTypeTraits.cpp
index 053a8baadf7b..d2825df0e842 100644
--- a/mfbt/tests/TestTypeTraits.cpp
+++ b/mfbt/tests/TestTypeTraits.cpp
@@ -86,45 +86,6 @@ TEST_IS_NOT_MEMBER_POINTER(int*)
 
 }  // namespace CPlusPlus11IsMemberPointer
 
-namespace CPlusPlus11IsScalar {
-
-using mozilla::IsScalar;
-
-enum E {};
-enum class EC {};
-class C {};
-struct S {};
-union U {};
-
-#define ASSERT_IS_SCALAR(type, msg) \
-  static_assert(IsScalar<type>::value, #type msg);
-#define TEST_IS_SCALAR(type) \
-  TEST_CV_QUALIFIERS(ASSERT_IS_SCALAR, type, " is a scalar type")
-
-TEST_IS_SCALAR(int)
-TEST_IS_SCALAR(float)
-TEST_IS_SCALAR(E)
-TEST_IS_SCALAR(EC)
-TEST_IS_SCALAR(S*)
-TEST_IS_SCALAR(int S::*)
-
-#undef TEST_IS_SCALAR
-#undef ASSERT_IS_SCALAR
-
-#define ASSERT_IS_NOT_SCALAR(type, msg) \
-  static_assert(!IsScalar<type>::value, #type msg);
-#define TEST_IS_NOT_SCALAR(type) \
-  TEST_CV_QUALIFIERS(ASSERT_IS_NOT_SCALAR, type, " is not a scalar type")
-
-TEST_IS_NOT_SCALAR(C)
-TEST_IS_NOT_SCALAR(S)
-TEST_IS_NOT_SCALAR(U)
-
-#undef TEST_IS_NOT_SCALAR
-#undef ASSERT_IS_NOT_SCALAR
-
-}  // namespace CPlusPlus11IsScalar
-
 static_assert(!IsSigned<bool>::value, "bool shouldn't be signed");
 static_assert(IsUnsigned<bool>::value, "bool should be unsigned");
 
diff --git a/xpcom/base/nsAutoPtr.h b/xpcom/base/nsAutoPtr.h
index eefab7294c38..7a0d557b5f1e 100644
--- a/xpcom/base/nsAutoPtr.h
+++ b/xpcom/base/nsAutoPtr.h
@@ -7,9 +7,10 @@
 #ifndef nsAutoPtr_h
 #define nsAutoPtr_h
 
+#include <type_traits>
+
 #include "nsCOMPtr.h"
 #include "mozilla/RefPtr.h"
-#include "mozilla/TypeTraits.h"
 
 #include "nsCycleCollectionNoteChild.h"
 #include "mozilla/MemoryReporting.h"
@@ -21,7 +22,7 @@
 template <class T>
 class nsAutoPtr {
  private:
-  static_assert(!mozilla::IsScalar<T>::value,
+  static_assert(!std::is_scalar_v<T>,
                 "If you are using "
                 "nsAutoPtr to hold an array, use UniquePtr<T[]> instead");