diff --git a/dom/base/FormData.cpp b/dom/base/FormData.cpp
index 9ad3da915a41..2370fb3bac44 100644
--- a/dom/base/FormData.cpp
+++ b/dom/base/FormData.cpp
@@ -18,7 +18,7 @@ using namespace mozilla;
 using namespace mozilla::dom;
 
 FormData::FormData(nsISupports* aOwner)
-  : HTMLFormSubmission(WrapNotNull(UTF_8_ENCODING), nullptr)
+  : HTMLFormSubmission(UTF_8_ENCODING, nullptr)
   , mOwner(aOwner)
 {
 }
@@ -402,7 +402,7 @@ NS_IMETHODIMP
 FormData::GetSendInfo(nsIInputStream** aBody, uint64_t* aContentLength,
                       nsACString& aContentTypeWithCharset, nsACString& aCharset)
 {
-  FSMultipartFormData fs(WrapNotNull(UTF_8_ENCODING), nullptr);
+  FSMultipartFormData fs(UTF_8_ENCODING, nullptr);
 
   for (uint32_t i = 0; i < mFormData.Length(); ++i) {
     if (mFormData[i].wasNullBlob) {
diff --git a/dom/html/HTMLFormSubmission.cpp b/dom/html/HTMLFormSubmission.cpp
index ad8acd0f44a6..0f62eecb5b80 100644
--- a/dom/html/HTMLFormSubmission.cpp
+++ b/dom/html/HTMLFormSubmission.cpp
@@ -889,7 +889,7 @@ GetSubmitEncoding(nsGenericHTMLElement* aForm)
   if (doc) {
     return Encoding::ForName(doc->GetDocumentCharacterSet());
   }
-  return WrapNotNull(UTF_8_ENCODING);
+  return UTF_8_ENCODING;
 }
 
 void
diff --git a/intl/Encoding.h b/intl/Encoding.h
index ef2f8b68cea5..123dee9aedcc 100644
--- a/intl/Encoding.h
+++ b/intl/Encoding.h
@@ -27,6 +27,7 @@ class Encoder;
 }; // namespace mozilla
 
 #define ENCODING_RS_ENCODING mozilla::Encoding
+#define ENCODING_RS_NOT_NULL_CONST_ENCODING_PTR mozilla::NotNull<const mozilla::Encoding*>
 #define ENCODING_RS_ENCODER mozilla::Encoder
 #define ENCODING_RS_DECODER mozilla::Decoder
 
diff --git a/intl/gtest/TestEncoding.cpp b/intl/gtest/TestEncoding.cpp
index 8c710c293b0a..a8d5d59c226f 100644
--- a/intl/gtest/TestEncoding.cpp
+++ b/intl/gtest/TestEncoding.cpp
@@ -4,11 +4,15 @@
 #include "gtest/gtest.h"
 
 #include "mozilla/Encoding.h"
+#include <type_traits>
 
 #define ENCODING_TEST(name) TEST(EncodingTest, name)
 
 using namespace mozilla;
 
+static_assert(std::is_standard_layout<NotNull<const Encoding*>>::value,
+              "NotNull<const Encoding*> must be a standard layout type.");
+
 // These tests mainly test that the C++ interface seems to
 // reach the Rust code. More thorough testing of the back
 // end is done in Rust.