How Case Sensitivity Broke My Build (and What I Learned)

How Case Sensitivity Broke My Build (and What I Learned)

A few days ago, I was working on a frontend project that had been building perfectly fine on my Mac. Everything looked smooth — no missing modules, no errors, no red lines, yada yada.
So I pushed it to GitHub and let my colleague handle the deployment through GitHub Actions.

But later, I received a message saying:

"Hey, the GitHub Actions build failed — something about a missing component called tooltip.jsx?"

That didn’t make sense. I opened the project folder, and sure enough, Tooltip.jsx was sitting right there. It had always been there.
So why was the Linux build freaking out?

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The Investigation

The error said:

CopyModule not found: Can't resolve './tooltip.jsx'

So I opened my repo and found the file:

CopyTooltip.jsx

Looks fine, right?
Except... notice the Capital T.
On my Mac, it built just fine, but on the Linux runner used by GitHub Actions, it failed.

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The Cause

==macOS and Windows are case-insensitive== — meaning:

CopyTooltip.jsx == tooltip.jsx

But Linux is case-sensitive, so:

CopyTooltip.jsx ≠ tooltip.jsx

They’re treated as two different files entirely.

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The Fix... Or So I Thought

I renamed the file to match the import, i.e., tooltip.jsx, pushed the commit, and asked my coworker to rerun the build.

But to my dismay came the following message...

"Still failing. Did you push the fix?"

I checked GitHub — and to my surprise, the same error was there.
But I was sure I renamed it. What gives?

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The Culprit

Turns out, Git doesn’t track case-only renames on case-insensitive systems like macOS.

So when I changed:

CopyTooltip.jsx → tooltip.jsx

Git basically went:

"Eh, looks the same to me."

and never registered the rename.
So the repo never updated, and the CI kept breaking.

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The Real Fix

Here’s how I finally beat it:

1. Rename the file temporarily
   This forces Git to register a name change.

   Copygit mv Tooltip.jsx tmp.jsx
   git commit -m "Temp rename to force case change"
   

2. Rename it again with the correct case

   Copygit mv tmp.jsx tooltip.jsx
   git commit -m "Fix case sensitivity issue"
   

3. Push your changes

   Copygit push
   

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Prevent This from Happening Again

If you often face case-sensitivity issues (especially when working between macOS/Windows and Linux), you can tell Git to track case changes explicitly:

Copygit config core.ignorecase false

Run this inside your repo to apply it locally, or add --global to make it apply to all your projects.

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Takeaway

If your builds mysteriously fail on Linux but work fine on your Mac or Windows machine — check your filenames.
Case mismatches can sneak up on you, and Git won’t always save you.

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Lesson learned:

What looks the same to you might not look the same to your CI.

Deploy on Nife

Ready to deploy? Check out the Nife documentation:

• GitHub Actions Deploy Guide
• Jenkins Deploy Guide