diff --git a/src/libqof/qof/qof-win32.c b/src/libqof/qof/qof-win32.c
index 6658bbfc0b..70933c612e 100644
--- a/src/libqof/qof/qof-win32.c
+++ b/src/libqof/qof/qof-win32.c
@@ -104,7 +104,7 @@ qof_win32_get_time_format(QofWin32Picture picture)
     case QOF_WIN32_PICTURE_DATETIME:
         tmp1 = get_win32_locale_string(LOCALE_SSHORTDATE);
         tmp2 = get_win32_locale_string(LOCALE_STIMEFORMAT);
-        locale_string = g_strconcat(tmp1, " ", tmp2);
+        locale_string = g_strconcat(tmp1, " ", tmp2, NULL);
         g_free(tmp1);
         g_free(tmp2);
         break;