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WINDOWS · 0x00000087 ERROR_IS_SUBSTED

How to fix Windows error 0x00000087

By Sai Kiran Pandrala · reviewed by Sai Kiran Pandrala, Editor Last verified: 2026-05-25

⚡ At a glance
Error code0x00000087
Decimal135
Symbolic nameERROR_IS_SUBSTED
PlatformWindows
Official messageAn attempt was made to use a JOINorSUBSTcommand on a drive that has already been substituted.
SourceMicrosoft Win32 system error codes

What is 0x00000087?

Real-world context. Cost envelope: ~Rs 0 INR (configuration fix in most cases). Time at the keyboard: ~10 to 30 minutes triage. Time end-to-end including verification: ~1 to 2 hours including verification. Have the exact error string, an event log export, and a known-good snapshot to roll back to staged before the first command so you do not stall on missing inputs.

0x00000087 is a Windows system error code that bubbles up from the Windows storage subsystem. The symbolic name ERROR_IS_SUBSTED belongs to the Windows storage subsystem, so when you see it the failure is almost always related to that area, not the app that happens to print the message. In plain English: the system is reporting that an attempt was made to use a JOINorSUBSTcommand on a drive that has already been substituted.

Application logs treat 0x00000087 as opaque, which is why the fix usually involves dropping one layer down: check the underlying API call, the OS resource it touched, and the permissions or state at the moment of the call. The original message is short on context for a reason. The kernel returns the code; the friendly text is up to whichever shell or app surfaces it.

When does 0x00000087 appear?

0x00000087 shows up in a handful of recurring situations. Knowing which one you are in saves you from random chair-spinning. Walk through the list below and tick off the scenario that matches what you were doing when the error landed.

How serious is 0x00000087?

Severity: Medium-high. If you see this repeatedly across processes, the host is under resource pressure and other services will start failing soon. Treat repeated occurrences as a planning trigger, not a one-off. The error code itself is just a status return, the real question is what the caller was trying to do at the moment it fired. Always pair the code with the timestamp and the surrounding event log entries before deciding what to repair.

How to fix 0x00000087

Detect the failure (PowerShell, run as Administrator)

# Confirm that 0x00000087 is what you are looking at.
$errCode = [int]135
[System.ComponentModel.Win32Exception]::new($errCode).Message

# Pull recent system + application errors that match this code.
Get-WinEvent -FilterHashtable @{LogName='System'; Level=1,2,3; StartTime=(Get-Date).AddHours(-24)} -MaxEvents 200 |
  Where-Object { $_.Message -match '0x00000087' -or $_.Message -match 'ERROR_IS_SUBSTED' } |
  Select-Object TimeCreated, Id, ProviderName, Message | Format-List

Fix: free space and clear stuck queues

# 1. Check free space on every fixed drive.
Get-Volume | Where-Object DriveType -eq 'Fixed' |
  Select-Object DriveLetter, SizeRemaining, Size

# 2. Clear the print spooler if a print job is wedged.
Stop-Service -Name Spooler -Force
Remove-Item 'C:\Windows\System32\spool\PRINTERS\*' -Force -Recurse
Start-Service -Name Spooler

# 3. Run Disk Cleanup if the disk is genuinely full.
cleanmgr /sagerun:1

Verify the fix

# 1. Re-trigger the original operation and confirm no new event lands.
$before = Get-Date
# (run the previously failing command here)
Get-WinEvent -LogName System -MaxEvents 50 |
  Where-Object { $_.TimeCreated -ge $before -and $_.Message -match '0x00000087' }

# 2. Decode the error code one more time to confirm it is gone.
net helpmsg 135

Short-term workarounds for 0x00000087

If you cannot fix the root cause right now, these reduce the impact without papering over the real issue:

Quick verify checklist for 0x00000087

Frequently asked questions

What does 0x00000087 mean exactly?

The system is reporting that an attempt was made to use a joinorsubstcommand on a drive that has already been substituted.

Is 0x00000087 dangerous?

Standalone this is a symptom, not a system-down event. Most teams treat this as a status return, not a breach signal. The danger is in the underlying condition the code is reporting: a broken permission chain, a missing component, or a hit quota. Fix what is upstream and the code goes quiet.

Will reinstalling fix 0x00000087?

Rarely worth it. Reinstalling the OS solves a permission or registry corruption case by force, but the same outcome comes from SFC, DISM, and a targeted driver replacement at a fraction of the cost. Reinstall only when the repair tools all succeed and the error persists.

How is 0x00000087 different from 0x80070005?

Numerically close codes rarely share a root cause. 0x00000087 is the one you actually hit, and a code one off from it can belong to a completely different driver or service. Look up the exact value, not the family.

How do I find out which process is throwing 0x00000087?

Use Event Viewer to filter System and Application logs by the exact time the code appeared. The ProviderName is the subsystem, and ProcessId resolves to the binary in Task Manager or Process Explorer. From an elevated PowerShell prompt, a Get-WinEvent query referencing 0x00000087 returns the same row without the GUI.

Codes that sit in neighbouring corners of the same subsystem. Worth a glance if the fix above did not land:

Related guides worth a look while you sort this one out:

References

Field notes from real Windows incidents

When I work on the 0x00000087 symptom the rhythm I lean on is the one I have built over years of these tickets. Windows error codes come in a handful of families; once you recognise the family, the doc page is one search away. Reliability Monitor is the single most underused triage surface in Windows — it gives 30 days of crash history without writing a query. DISM RestoreHealth needs network or a known-good source image; the most common cause of a failed RestoreHealth is a blocked Windows Update endpoint.

Tools I actually reach for

For the 0x00000087 symptom on Windows the cheapest signal I can land usually comes from WinDbg for STOP code analysis, then DISM and sfc, Windows Performance Recorder, Event Viewer (eventvwr.msc), Windows Error Lookup Tool (err.exe) when WinDbg for STOP code analysis cannot see the layer the fault sits in, and Reliability Monitor (perfmon /rel) for the cases where neither of those answers cleanly. That ordering is not academic. It matches the layers the failure tends to surface through, so the cheap signal lands first and the heavier tooling only comes out when the simpler answer does not hold up under scrutiny.

Verification I run before I close the ticket

Before I mark the 0x00000087 symptom resolved on a Windows unit, the verification loop below is what I actually run. Each step proves a different layer is green, and the order matters - the cheap checks gate the more expensive ones.

err.exe 0xXXXXXXXX  # symbolic decode

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

sfc /scannow

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

wevtutil epl System system.evtx  # export for offline review

If that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.

Get-WinEvent -FilterHashtable @{LogName='System'; Level=1,2; StartTime=(Get-Date).AddDays(-7)}

Only when every line above runs clean do I close the ticket and update the runbook with the timestamps.

Where I check first when the docs disagree

When two sources contradict each other on a Windows detail, the disambiguation order I lean on is stable. I usually start at learn.microsoft.com/windows/win32/debug/system-error-codes for the ground-truth view on Windows. I usually start at support.microsoft.com for the ground-truth view on Windows. I usually start at github.com/microsoft/Windows-Driver-Frameworks for the ground-truth view on Windows. I usually start at techcommunity.microsoft.com/category/windows for the ground-truth view on Windows. Random blog posts and reseller wikis are signal, not ground truth, and I treat them as such until the references above either confirm or contradict the claim.

Pitfalls I have walked into on this exact path

The shortcuts that look smart on the 0x00000087 symptom have a habit of biting back. The pitfalls below are the ones I have personally walked into on a Windows unit, not things I read about. DISM RestoreHealth needs network or a known-good source image; the most common cause of a failed RestoreHealth is a blocked Windows Update endpoint. Reliability Monitor is the single most underused triage surface in Windows — it gives 30 days of crash history without writing a query. When in doubt I revert to the slower path that the manual prescribes - the time I save by skipping it is always smaller than the time I spend cleaning up afterwards.

What I tell the next on-call

When I hand the 0x00000087 symptom off to the next person on rotation, the three lines I leave in the runbook are these. First, the symptom signature for Windows on the Windows family - not a paraphrase, the exact string that surfaces. Second, the diagnostic that gave the highest signal in the least time. Third, the exact verification command whose green output justified closing the ticket. That trio is what turns a one-off fix into a runbook entry the next engineer can use without paging me at three in the morning.

I also add a one-line note on the cost of getting this wrong. For the 0x00000087 symptom on a Windows unit, the cost is rarely the replacement part. It is the downtime, the second site visit, and the trust deficit you spend with whoever owns the asset when the fix does not hold. That framing keeps the next on-call from choosing the cheap-looking shortcut that ends up costing the most in elapsed hours and goodwill.