diff --git a/src/SFML/Audio/SoundFileFactory.cpp b/src/SFML/Audio/SoundFileFactory.cpp
index a9d1478000..107a54deea 100644
--- a/src/SFML/Audio/SoundFileFactory.cpp
+++ b/src/SFML/Audio/SoundFileFactory.cpp
@@ -39,6 +39,7 @@
 #include <SFML/System/MemoryInputStream.hpp>
 #include <SFML/System/Utils.hpp>
 
+#include <mutex>
 #include <ostream>
 
 
@@ -47,18 +48,18 @@ namespace
 // Register all the built-in readers and writers if not already done
 void ensureDefaultReadersWritersRegistered()
 {
-    static bool registered = false;
-    if (!registered)
-    {
-        sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderFlac>();
-        sf::SoundFileFactory::registerWriter<sf::priv::SoundFileWriterFlac>();
-        sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderMp3>();
-        sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderOgg>();
-        sf::SoundFileFactory::registerWriter<sf::priv::SoundFileWriterOgg>();
-        sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderWav>();
-        sf::SoundFileFactory::registerWriter<sf::priv::SoundFileWriterWav>();
-        registered = true;
-    }
+    static std::once_flag flag;
+    std::call_once(flag,
+                   []()
+                   {
+                       sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderFlac>();
+                       sf::SoundFileFactory::registerWriter<sf::priv::SoundFileWriterFlac>();
+                       sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderMp3>();
+                       sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderOgg>();
+                       sf::SoundFileFactory::registerWriter<sf::priv::SoundFileWriterOgg>();
+                       sf::SoundFileFactory::registerReader<sf::priv::SoundFileReaderWav>();
+                       sf::SoundFileFactory::registerWriter<sf::priv::SoundFileWriterWav>();
+                   });
 }
 } // namespace