diff --git a/modules/rosapps/applications/screensavers/butterflies/butterflies.c b/modules/rosapps/applications/screensavers/butterflies/butterflies.c
index 1c181fea912..60f7ed4d171 100644
--- a/modules/rosapps/applications/screensavers/butterflies/butterflies.c
+++ b/modules/rosapps/applications/screensavers/butterflies/butterflies.c
@@ -230,7 +230,7 @@ void Display()
 
 }
 
-INT_PTR AboutProc(HWND hdlg, UINT msg, WPARAM wpm, LPARAM lpm){
+INT_PTR CALLBACK AboutProc(HWND hdlg, UINT msg, WPARAM wpm, LPARAM lpm){
     
 	switch(msg){
 	case WM_CTLCOLORSTATIC: