1. Until https://github.com/CSSLint/parser-lib/issues/229 is fixed, manually replace: while (lt !== Tokens.COMMA && lt !== Tokens.S && lt !== Tokens.RPAREN) { in "_function: function()" with while (lt !== Tokens.COMMA && lt !== Tokens.S && lt !== Tokens.RPAREN && lt !== Tokens.EOF) { 2. Apply our hacks unless supported natively (use git history for the file as this warning may be obsolete): * 449a27cc Add CSSLint position sticky rule * d49e44dd CSS variables * 2e86c958 fire startdocument on { * bc63ecca support "i" in attribute selector * 2468784e fix crashing on unclosed calc() at eof * 3287b79f Support :any(), :-webkit-any(), :-moz-any() * 4684016a Support @supports inside @-moz-document