diff --git a/openvpn.c b/openvpn.c
index 29d82d9..4df60fa 100644
--- a/openvpn.c
+++ b/openvpn.c
@@ -240,7 +240,7 @@ UserAuthDialogFunc(HWND hwndDlg, UINT msg, WPARAM wParam, LPARAM lParam)
 
             /* Clear buffers */
             memset(buf, 'x', sizeof(buf));
-            buf[sizeof(buf) - 1] = _T('\0');
+            buf[_tsizeof(buf) - 1] = _T('\0');
             SetDlgItemText(hwndDlg, ID_EDT_AUTH_USER, buf);
             SetDlgItemText(hwndDlg, ID_EDT_AUTH_PASS, buf);
 
@@ -297,7 +297,7 @@ PrivKeyPassDialogFunc(HWND hwndDlg, UINT msg, WPARAM wParam, LPARAM lParam)
 
             /* Clear buffer */
             memset(buf, 'x', sizeof(buf));
-            buf[sizeof(buf) - 1] = _T('\0');
+            buf[_tsizeof(buf) - 1] = _T('\0');
             SetDlgItemText(hwndDlg, ID_EDT_PASSPHRASE, buf);
 
             EndDialog(hwndDlg, LOWORD(wParam));
diff --git a/proxy.c b/proxy.c
index ce2a57e..8004bca 100644
--- a/proxy.c
+++ b/proxy.c
@@ -357,7 +357,7 @@ ProxyAuthDialogFunc(HWND hwndDlg, UINT msg, WPARAM wParam, LPARAM lParam)
 
             /* Clear buffers */
             memset(buf, 'x', sizeof(buf));
-            buf[sizeof(buf) - 1] = _T('\0');
+            buf[_tsizeof(buf) - 1] = _T('\0');
             SetDlgItemText(hwndDlg, ID_EDT_PROXY_USER, buf);
             SetDlgItemText(hwndDlg, ID_EDT_PROXY_PASS, buf);