diff --git a/folly/FixedString.h b/folly/FixedString.h
index 2f817a7b8d9..0eb7d18dd1b 100644
--- a/folly/FixedString.h
+++ b/folly/FixedString.h
@@ -2900,7 +2900,7 @@ constexpr const std::size_t& npos = detail::fixedstring::FixedStringBase::npos;
  *   `FixedString<8>`, `FixedString<16>`, etc.
  */
 template <class Char, Char... Cs>
-constexpr BasicFixedString<Char, sizeof...(Cs)> operator"" _fs() noexcept {
+constexpr BasicFixedString<Char, sizeof...(Cs)> operator""_fs() noexcept {
   const Char a[] = {Cs..., Char(0)};
   return {+a, sizeof...(Cs)};
 }
@@ -2909,7 +2909,7 @@ constexpr BasicFixedString<Char, sizeof...(Cs)> operator"" _fs() noexcept {
 #endif
 
 #define FOLLY_DEFINE_FIXED_STRING_UDL(N)                     \
-  constexpr FixedString<N> operator"" _fs##N(                \
+  constexpr FixedString<N> operator""_fs##N(                 \
       const char* that, std::size_t count) noexcept(false) { \
     return {that, count};                                    \
   }                                                          \
diff --git a/folly/system/Shell.h b/folly/system/Shell.h
index f0cd43784fc..c80e68d8924 100644
--- a/folly/system/Shell.h
+++ b/folly/system/Shell.h
@@ -61,7 +61,7 @@ struct ShellCmdFormat {
 
 inline namespace literals {
 inline namespace shell_literals {
-constexpr detail::ShellCmdFormat operator"" _shellify(
+constexpr detail::ShellCmdFormat operator""_shellify(
     char const* name, std::size_t length) {
   return {folly::StringPiece(name, length)};
 }