Textualize/textual · error · StyleValueError

unknown word {word!r} in style flags

Error message

unknown word {word!r} in style flags

What it means

StyleFlagsProperty (used by rules like `text-style`) validates each whitespace-separated word against VALID_STYLE_FLAGS before delegating to rich's Style.parse. Unknown words — including misspelled flags or non-Textual web CSS keywords — raise StyleValueError naming the word.

Source

Thrown at src/textual/css/_style_properties.py:1094

            style_flags: The style flags to set as a string. For example,
                ``"bold italic"``.

        Raises:
            StyleValueError: If the value is an invalid style flag.
        """
        _rich_traceback_omit = True
        if style_flags is None:
            if obj.clear_rule(self.name):
                obj.refresh(children=True)
        elif isinstance(style_flags, Style):
            if obj.set_rule(self.name, style_flags):
                obj.refresh(children=True)
        else:
            words = [word.strip() for word in style_flags.split(" ")]
            valid_word = VALID_STYLE_FLAGS.__contains__
            for word in words:
                if not valid_word(word):
                    raise StyleValueError(
                        f"unknown word {word!r} in style flags",
                        help_text=style_flags_property_help_text(
                            self.name, word, context="inline"
                        ),
                    )
            try:
                style = Style.parse(style_flags)
            except rich.errors.StyleSyntaxError as error:
                if "none" in words and len(words) > 1:
                    raise StyleValueError(
                        "cannot mix 'none' with other style flags",
                        help_text=style_flags_property_help_text(
                            self.name, " ".join(words), context="inline"
                        ),
                    ) from None
                raise error from None
            if obj.set_rule(self.name, style):
                obj.refresh(children=True)

View on GitHub (pinned to 06dbeef4bb)

Solutions

1. Use only documented style flags, separated by spaces
2. Check the VALID_STYLE_FLAGS set for your installed version if unsure

Example fix

# before
styles.text_style = "bold ittalic"
# after
styles.text_style = "bold italic"

from textual.css.constants import VALID_STYLE_FLAGS
words = value.split()
if all(w in VALID_STYLE_FLAGS for w in words):
    styles.text_style = value

When it happens

Trigger: `styles.text_style = "bold ittalic"`, `styles.text_style = "underline2"` (if unsupported in that version), or `text-style: strike;` in TCSS. Valid flags include bold, italic, underline, reverse, none, etc.

Common situations: Typos, mixing in rich-only or web-CSS keywords, or flags removed/renamed across Textual versions.

Related errors

• {self.name} must be one of {friendly_list(self._valid_values
• cannot mix 'none' with other style flags
• Expected a str, Path or list[str | Path] for the CSS_PATH.
• {self.name} must be a str
• invalid percentage value '{token}'

AI-assisted analysis of Textualize/textual@06dbeef4bb (2026-08-27). Data as JSON: /api/errors/53177a0fea169a8c. Report an issue: GitHub.