diff --git a/src/SFML/Window/GlResource.cpp b/src/SFML/Window/GlResource.cpp
index a0fa41aa..c3f26384 100644
--- a/src/SFML/Window/GlResource.cpp
+++ b/src/SFML/Window/GlResource.cpp
@@ -38,7 +38,6 @@ namespace
 {
     // OpenGL resources counter and its mutex
     unsigned long count = 0;
-    bool initialized = false;
     sf::Mutex mutex;
 }
 
diff --git a/src/SFML/Window/WindowImpl.cpp b/src/SFML/Window/WindowImpl.cpp
index 51f73b33..9e863e2f 100644
--- a/src/SFML/Window/WindowImpl.cpp
+++ b/src/SFML/Window/WindowImpl.cpp
@@ -28,6 +28,7 @@
 #include <SFML/Window/WindowImpl.hpp>
 #include <SFML/Window/Event.hpp>
 #include <SFML/Window/JoystickManager.hpp>
+#include <SFML/System/Sleep.hpp>
 #include <algorithm>
 #include <cmath>