diff --git a/robotgo.go b/robotgo.go
index 8408840..e0ebc45 100644
--- a/robotgo.go
+++ b/robotgo.go
@@ -987,5 +987,5 @@ func FindIds(name string) ([]int32, error) {
 
 // ActivePID window active by PID
 func ActivePID(pid int32) {
-	C.active_PID(C.int32(pid))
+	C.active_PID(C.uintptr(pid))
 }
diff --git a/window/goWindow.h b/window/goWindow.h
index 4ae5a72..1b1f9f7 100644
--- a/window/goWindow.h
+++ b/window/goWindow.h
@@ -57,15 +57,15 @@ void aSetActive(const MData win){
 	SetActive(win);
 }
 
-void active_PID(int32 pid){
+void active_PID(uintptr pid){
 	MData win;
 	#if defined(IS_MACOSX)
 		// Handle to a AXUIElementRef
 		win.AxID = AXUIElementCreateApplication(pid);
 	#elif defined(USE_X11)
-		win.XWin = pid;		// Handle to an X11 window
+		win.XWin = (Window) pid;		// Handle to an X11 window
 	#elif defined(IS_WINDOWS)
-		win.HWnd = HWND(pid);		// Handle to a window HWND
+		win.HWnd = (HWND) pid;		// Handle to a window HWND
 	#endif
 	SetActive(win);
 }