Software⏱️ 3 min read📅 2026-06-11

How to Fix: Checking Firefox version using cmd returns an error

Error checking Firefox version using cmd returns assertion failure and display not specified.

Quick Answer: Check the system page size configuration, as it can cause issues with Firefox version checking.

📋 Table of Contents

  1. 💡 Why You Are Getting This Error
  2. ✅ Best Solutions to Fix It
  3. ✨ Wrapping Up

The error '(process:12746): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed' is encountered when running Firefox version checking command using cmd. This issue affects users who are trying to check the version of Firefox on their system.

This error can be frustrating for developers and testers as it prevents them from accurately verifying the version of Firefox installed on their system, which can lead to issues in Selenium tests.

💡 Why You Are Getting This Error

  • The primary reason for this error is that the system page size has been set to 0, causing a critical assertion failure. This issue occurs when the g_slice_set_config function fails due to an invalid sys_page_size value.
  • Another possible cause of this error is related to the display settings. The error 'Error: no display specified' suggests that Firefox is unable to connect to a display device, which can be caused by issues with the X11 server or display configuration.

✅ Best Solutions to Fix It

Resetting System Page Size

  1. Step 1: Step 1: Open the Command Prompt as an administrator and run the command 'fsadm -c 0' to reset the system page size to its default value.
  2. Step 2: Step 2: Run the command 'fsadm -c 0' again to confirm that the system page size has been successfully reset.
  3. Step 3: Step 3: Check if Firefox version checking is successful by running the command 'firefox -v' again.

Enabling X11 Display

  1. Step 1: Step 1: Open the Terminal and run the command 'XDG_SESSION_TYPE=xdmcp xrandr --server 12 --outputnone' to enable X11 display.
  2. Step 2: Step 2: Run the command 'firefox -v' again to check if Firefox version checking is successful.

✨ Wrapping Up

To resolve this issue, try resetting the system page size or enabling X11 display. If neither method works, it may be necessary to reinstall Firefox or seek further assistance from a system administrator.

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