diff --git a/include/SFML/System/Sleep.hpp b/include/SFML/System/Sleep.hpp
index 8cc23f52..f131d934 100644
--- a/include/SFML/System/Sleep.hpp
+++ b/include/SFML/System/Sleep.hpp
@@ -36,7 +36,7 @@ namespace sf
     ////////////////////////////////////////////////////////////
     /// Make the current thread sleep for a given time
     ///
-    /// \param Duration : Time to sleep, in seconds
+    /// \param Duration : Time to sleep, in seconds (must be >= 0)
     ///
     ////////////////////////////////////////////////////////////
     void SFML_API Sleep(float Duration);
diff --git a/src/SFML/System/Sleep.cpp b/src/SFML/System/Sleep.cpp
index 1c220541..a984db01 100644
--- a/src/SFML/System/Sleep.cpp
+++ b/src/SFML/System/Sleep.cpp
@@ -36,7 +36,8 @@ namespace sf
 ////////////////////////////////////////////////////////////
 void Sleep(float Duration)
 {
-    priv::Platform::Sleep(Duration);
+    if (Duration >= 0)
+        priv::Platform::Sleep(Duration);
 }
 
 } // namespace sf