diff --git a/src/os_mswin.c b/src/os_mswin.c
index 839c3df..b4f662a 100644
--- a/src/os_mswin.c
+++ b/src/os_mswin.c
@@ -1869,7 +1869,7 @@
 
 #ifndef FEAT_GUI
 
-    static UINT CALLBACK
+    static UINT_PTR CALLBACK
 PrintHookProc(
 	HWND hDlg,	// handle to dialog box
 	UINT uiMsg,	// message identifier