SUMMARY STEPS TO REPRODUCE 1. Log into a Windows machine with the code page set to 437. 2. Download "Wireshark User’s Guide.epub" from https://www.wireshark.org/download/docs/. 3. Try to open the file in Okular. OBSERVED RESULT Okular displays the error "Could not open file:///C:/path/to/Wireshark User's Guide.epub. Error while opening the EPub document." EXPECTED RESULT Okular should be able to open a file with U+2019 RIGHT SINGLE QUOTATION MARK in its name, such as "Wireshark User’s Guide.epub". The file opens just fine if I replace the curly quote with an apostrophe ('). SOFTWARE/OS VERSIONS Windows: Server 2019 1809 ADDITIONAL INFORMATION This might be due to the fact that Qt mangles command line arguments with extended characters on Windows: https://bugreports.qt.io/browse/QTBUG-46118 https://github.com/qt/qtbase/blob/6.2/src/corelib/kernel/qcoreapplication.cpp#L172 We worked around this in Wireshark by fetching the wide version of the argument vector and converting it to UTF-8 on Windows: https://gitlab.com/wireshark/wireshark/-/blob/0a9ef601/ui/qt/main.cpp#L562