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What is the current behavior?

When I have style-loader in my CSS loaders chain, the source maps do not work in Firefox. I see error messages in the Developer Tools console like the one below. Setting convertToAbsoluteUrls: true doesn't change the situation.

Source map error: Error: sourceMapURL could not be parsed Resource URL: blob:http://localhost:8080/3a52944e-4117-4d8d-98d6-32cd525beae9 Source Map URL: data:application/json;base64,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[Learn More]

When I remove style-loader and use extract-text-webpack-plugin instead, the source maps start to work. In addition even if style-loader is used, everything works fine in Chrome Developer Tools.

I created an example repo with the problem: https://github.com/robertjk/webpack-firefox-source-map-error.

What is the expected behavior?

I expect source maps to work properly in Firefox, as they do when style-loader is not used.

Additional info

Firefox version: 59.0b8
Node.js verison: 9.5.0
webpack version: 3.11.0
style-loader version: 0.20.1