diff --git a/redo/common_windows.go b/redo/common_windows.go
index 38a5510..3ec4ddd 100644
--- a/redo/common_windows.go
+++ b/redo/common_windows.go
@@ -21,6 +21,11 @@ func xpanichresult(msg *C.char, hresult C.HRESULT) {
 	panic(fmt.Errorf("%s; HRESULT: 0x%X", C.GoString(msg), hresult))
 }
 
+//export xpaniccomdlg
+func xpaniccomdlg(msg *C.char, err C.DWORD) {
+	panic(fmt.Errorf("%s; comdlg32.dll extended error: 0x%X", C.GoString(msg), err))
+}
+
 //export xmissedmsg
 func xmissedmsg(purpose *C.char, f *C.char, uMsg C.UINT) {
 	panic(fmt.Errorf("%s window procedure message %d does not return a value (bug in %s)", C.GoString(purpose), uMsg, C.GoString(f)))
diff --git a/redo/dialog_windows.c b/redo/dialog_windows.c
index fff8e95..8b942f3 100644
--- a/redo/dialog_windows.c
+++ b/redo/dialog_windows.c
@@ -47,7 +47,7 @@ WCHAR *openFile(void)
 		err = CommDlgExtendedError();
 		if (err == 0)				// user cancelled
 			return NULL;
-		xpanic("error running open file dialog", GetLastError());
+		xpaniccomdlg("error running open file dialog", err);
 	}
 	return filenameBuffer;
 }