diff --git a/source/Platform/PlatformEventQueue.h b/source/Platform/PlatformEventQueue.h
index d6c92a6..8a443e6 100644
--- a/source/Platform/PlatformEventQueue.h
+++ b/source/Platform/PlatformEventQueue.h
@@ -3,6 +3,8 @@
 
 namespace sp {
 
+struct SysEvent;
+
 // Interface for platform specific event queue.
 class PlatformEventQueue
 {