In source/gjs/modules/dbus.js the variable expectedNumberArgs is used in an error message at lines 77 and 80. However, this variable does not exist; minNumberArgs should be used instead.

This is the affected code:

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let signatureLength = this.signatureLength(inSignature);
    let minNumberArgs = signatureLength;
    let maxNumberArgs = signatureLength + 2;

    if (arg_array.length < minNumberArgs) {
        throw new Error("Not enough arguments passed for method: " + methodName +
                       ". Expected " + expectedNumberArgs + ", got " + arg_array.length);
    } else if (arg_array.length > maxNumberArgs) {
        throw new Error("Too many arguments passed for method: " + methodName +
                       ". Maximum is " + expectedNumberArgs +
                        " + one callback and/or flags");
    }
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When it gets invoked, the error «JS ERROR: !!! Exception was: ReferenceError: expectedNumberArgs is not defined» is printed. Changing expdectedNumberArgs to minNumberArgs the code works as expected.