diff --git a/se/se_epub_lint.py b/se/se_epub_lint.py
index 61803c8a..c2d7fc31 100644
--- a/se/se_epub_lint.py
+++ b/se/se_epub_lint.py
@@ -146,6 +146,7 @@
 "c-024", "Illegal unit used to set [css]line-height[/]. Hint: [css]line-height[/] is set without any units."
 "c-025", "Illegal percent unit used to set [css]height[/] or positioning property. Hint: [css]vh[/] to specify vertical-oriented properties like height or position."
 "c-026", "Table that appears to be listing numbers, but without [css]font-variant-numeric: tabular-nums;[/]."
+"c-027", "Font size below 1."
 
 FILESYSTEM
 "f-001", "Illegal file or directory."
@@ -1120,6 +1121,10 @@ def _lint_css_checks(self, local_css_path: Path, abbr_with_whitespace: list) ->
 	if matches:
 		messages.append(LintMessage("c-025", "Illegal percent unit used to set [css]height[/] or positioning property. Hint: [css]vh[/] to specify vertical-oriented properties like height or position.", se.MESSAGE_TYPE_ERROR, local_css_path))
 
+	matches = regex.search(r"font-size: \.", self.local_css)
+	if matches:
+		messages.append(LintMessage("c-027", "Font size below 1.", se.MESSAGE_TYPE_ERROR, local_css_path))
+
 	return messages
 
 def _update_missing_styles(filename: Path, dom: se.easy_xml.EasyXmlTree, local_css: dict) -> list: