diff --git a/src/gui/Window.cc b/src/gui/Window.cc
index d3aaf44..ffef3c5 100644
--- a/src/gui/Window.cc
+++ b/src/gui/Window.cc
@@ -218,7 +218,11 @@ void Window::handle_keypress(uint32_t keyval)
 {
     uint32_t ctrl_keyval = keyval & (JTK_KEY_KEYCODE_MASK | JTK_KEY_MODS_CTRL);
     uint32_t keycode = keyval & JTK_KEY_KEYCODE_MASK;
-    if (m_focused_buffer_pane->insert_mode())
+    if ((JTK_KEY_SHIFT_L <= keycode) && (keycode <= JTK_KEY_SUPER_R))
+    {
+        /* Ignore modifier key presses. */
+    }
+    else if (m_focused_buffer_pane->insert_mode())
     {
         if (keycode == '\033')
         {