Mac OS 10.14 Mojave + qt5.5 + gem capybara-webkit

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My config is MAC Mojave v10.14.

I try to install gem Capybara-webkit -v '1.15.0' which need qt5.5, but qt5.5 has been dropped of the homebrew and it is not compatible with Xcode v10.

I try this :

  • Uninstall Xcode v10
  • Install Xcode 9.4.1, found in
  • Install qt5.5, I have found it in the archives on
  • Run bundle

But it fail, my error is with the gem capybara-webkit -v '1.15.0':

Fetching capybara-webkit 1.15.0
Installing capybara-webkit 1.15.0 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

current directory: 
/Users/thomas/.rbenv/versions/2.4.4/bin/ruby -r ./siteconf20181005-763-1bppnfh.rb extconf.rb
Project ERROR: Xcode not set up properly. You may need to confirm the license agreement by running /usr/bin/xcodebuild.
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
Command 'qmake ' failed

extconf failed, exit code 1

 Gem files will remain installed in 
/Users/thomas/.rbenv/versions/2.4.4/lib/ruby/gems/2.4.0/gems/capybara-webkit-1.15.0 for inspection.
Results logged to /Users/thomas/.rbenv/versions/2.4.4/lib/ruby/gems/2.4.0/extensions/x86_64- darwin-18/2.4.0-static/capybara-webkit-1.15.0/gem_make.out

An error occurred while installing capybara-webkit (1.15.0), and Bundler 
cannot continue.
Make sure that `gem install capybara-webkit -v '1.15.0' --source 
''` succeeds before bundling.

In Gemfile:

Next, I did:

sudo xcodebuild -license agree

But the error persists...

Thank you for your help !

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As described on the capybara-webkit wiki, capybara-webkit depends on Qt 5.5. "Qt 5.5 is the last version of Qt that capybara-webkit will support. The Qt project has dropped the WebKit bindings from binary releases in 5.6."

To install Qt 5.5 follow the instructions from the wiki. For Mojave, the instructions are the following.

brew update
cd $( brew --prefix )/Homebrew/Library/Taps/homebrew/homebrew-core
git checkout 9ba3d6ef8891e5c15dbdc9333f857b13711d4e97 Formula/qt@5.5.rb
brew install qt@5.5
echo 'export PATH="$(brew --prefix qt@5.5)/bin:$PATH"' >> ~/.bashrc

You can confirm this step worked by running:

$ which qmake

Next, you need to install Xcode 9.4. Xcode 10 is not compatible with Qt 5.5. Xcode 9.4 can be downloaded from the Apple developer portal. This is a 4GB download and takes about 30 minutes to download and install. You can verify it's correctly installed by running the following:

$ /usr/bin/xcodebuild -version
Xcode 9.4.1
Build version 9F2000

If this doesn't work, it may be because you have only the Command Line Tools installed instead of Xcode, in which case you should make sure you downloaded the right version of Xcode. Or the Xcode folder may set incorrectly. If so, you can fix this using xcode-select, which will specifiy the folder in which xcodebuild runs:

sudo xcode-select -s /Applications/

When Xcode is finally installed, locate it in your Applications folder, open it, and agree to the license. Then try reinstalling capybara-webkit.

Disclaimer: I came up with the above answer from compiling multiple questions and answers and trying to remember the order in which I ran commands on my local machine. I may have accidentally omitted some steps.

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You need Xcode 9.4.1 to install qt@5.5 as it's not compatible with Xcode 10. Homebrew has deleted the qt@5.5 from their core tap so to install it you need to run the following before:

brew update
cd $( brew --prefix )/Homebrew/Library/Taps/homebrew/homebrew-core
git checkout 9ba3d6ef8891e5c15dbdc9333f857b13711d4e97 Formula/qt@5.5.rb
brew install qt@5.5

9ba3d6ef8891e5c15dbdc9333f857b13711d4e97 is the parent commit of 360923286c0f1a6a1325ada578df030bf579009f where they removed qt@5.5 so this command rollbacks to the parent commit and checkout the needed formula file.

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I could install qt@5.5 on Mojave with this:

brew install qt@5.5 --force-bottle

With capybara-webkit, I temporarily use this:

gem "capybara-webkit", git: "", ref: "9c9af833656f095667e8522004dae017d423d37d"

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  • Please post your solution as an answer to your question. You can then accept your own answer. That way it is easier for people to search if they have similar issues.
  • What's annoying now is they removed Qt 5.5 from their website. Link is broken
  • The full manual here… It has useful notes. Helped me to install capybara-webkit on Mojave
  • I get an error running brew install qt@5.5 on OS X Mojave: Error: qt@5.5: unknown version :mountain_lion - following the update here:… seems to have resolved the problem
  • I still have problems to install Qt5.5. ../src/corelib/global/qglobal.h:39:12: fatal error: 'cstddef' file not found # include <cstddef>
  • Are you using home brew?
  • Yes, I have reinstall Mojave from scratch and install Xcode 9.4.1 and follow this steps but I still unlucky. I got the message that Xcode and CommandLineTools are outdated so I can install qt@5.5.
  • NOTE: If you got error fatal: reference is not a tree: 9ba3d6ef8891e5c15dbdc9333f857b13711d4e97, use git fetch --unshallow to complete git history. NOTE: If you get Error: qt@5.5: unknown version :mountain_lion, comment line #25 in Formula/qt@5.5.rb More details:…
  • This didn't work for me. ``` Error: No available formula with the name "qt@5.5" ==> Searching for a previously deleted formula (in the last month)... qt@5.5 was deleted from homebrew/core in commit 360923286c: qt@5.5: delete ```