diff --git a/mfbt/Literals.h b/mfbt/Literals.h
index d1d403afaeb3..97f24af8003f 100644
--- a/mfbt/Literals.h
+++ b/mfbt/Literals.h
@@ -16,19 +16,19 @@
 //
 // size_t page_size = 4_KiB;
 //
-constexpr size_t operator"" _KiB(unsigned long long int aNum) {
+constexpr size_t operator""_KiB(unsigned long long int aNum) {
   return size_t(aNum) * 1024;
 }
 
-constexpr size_t operator"" _KiB(long double aNum) {
+constexpr size_t operator""_KiB(long double aNum) {
   return size_t(aNum * 1024);
 }
 
-constexpr size_t operator"" _MiB(unsigned long long int aNum) {
+constexpr size_t operator""_MiB(unsigned long long int aNum) {
   return size_t(aNum) * 1024_KiB;
 }
 
-constexpr size_t operator"" _MiB(long double aNum) {
+constexpr size_t operator""_MiB(long double aNum) {
   return size_t(aNum * 1024_KiB);
 }
 
diff --git a/xpcom/string/nsTLiteralString.h b/xpcom/string/nsTLiteralString.h
index 0d14614583d2..7d15b695478d 100644
--- a/xpcom/string/nsTLiteralString.h
+++ b/xpcom/string/nsTLiteralString.h
@@ -91,8 +91,8 @@ class nsTLiteralString : public mozilla::detail::nsTStringRepr<T> {
 // any non-private use of that constructor would get into the codebase.
 #if defined(__clang__)
  private:
-  friend constexpr auto operator"" _ns(const char* aStr, std::size_t aLen);
-  friend constexpr auto operator"" _ns(const char16_t* aStr, std::size_t aLen);
+  friend constexpr auto operator""_ns(const char* aStr, std::size_t aLen);
+  friend constexpr auto operator""_ns(const char16_t* aStr, std::size_t aLen);
 #else
  public:
 #endif