diff --git a/Kernel/TTY/MasterPTY.cpp b/Kernel/TTY/MasterPTY.cpp
index cace566a99..efd29a7f27 100644
--- a/Kernel/TTY/MasterPTY.cpp
+++ b/Kernel/TTY/MasterPTY.cpp
@@ -98,6 +98,8 @@ void MasterPTY::close()
 
 int MasterPTY::ioctl(FileDescription& description, unsigned request, unsigned arg)
 {
+    if (!m_slave)
+        return -EIO;
     if (request == TIOCSWINSZ || request == TIOCGPGRP)
         return m_slave->ioctl(description, request, arg);
     return -EINVAL;