diff --git a/components/style/values/generics/font.rs b/components/style/values/generics/font.rs
index 02f91068d38..a88df7be173 100644
--- a/components/style/values/generics/font.rs
+++ b/components/style/values/generics/font.rs
@@ -207,6 +207,7 @@ pub enum FontStyle<Angle> {
 ///
 /// https://www.w3.org/TR/css-fonts-4/#font-size-adjust-prop
 /// https://github.com/w3c/csswg-drafts/issues/6160
+/// https://github.com/w3c/csswg-drafts/issues/6288
 #[allow(missing_docs)]
 #[repr(u8)]
 #[derive(
@@ -228,14 +229,16 @@ pub enum FontStyle<Angle> {
 pub enum GenericFontSizeAdjust<Number> {
     #[animation(error)]
     None,
-    // 'ex' is the implied basis, so the keyword can be omitted
-    Ex(Number),
+    // 'ex-height' is the implied basis, so the keyword can be omitted
+    ExHeight(Number),
     #[value_info(starts_with_keyword)]
-    Cap(Number),
+    CapHeight(Number),
     #[value_info(starts_with_keyword)]
-    Ch(Number),
+    ChWidth(Number),
     #[value_info(starts_with_keyword)]
-    Ic(Number),
+    IcWidth(Number),
+    #[value_info(starts_with_keyword)]
+    IcHeight(Number),
 }
 
 impl<Number: ToCss> ToCss for GenericFontSizeAdjust<Number> {
@@ -245,10 +248,11 @@ impl<Number: ToCss> ToCss for GenericFontSizeAdjust<Number> {
     {
         let (prefix, value) = match self {
             Self::None => return dest.write_str("none"),
-            Self::Ex(v) => ("", v),
-            Self::Cap(v) => ("cap ", v),
-            Self::Ch(v) => ("ch ", v),
-            Self::Ic(v) => ("ic ", v),
+            Self::ExHeight(v) => ("", v),
+            Self::CapHeight(v) => ("cap-height ", v),
+            Self::ChWidth(v) => ("ch-width ", v),
+            Self::IcWidth(v) => ("ic-width ", v),
+            Self::IcHeight(v) => ("ic-height ", v),
         };
 
         dest.write_str(prefix)?;
diff --git a/components/style/values/specified/font.rs b/components/style/values/specified/font.rs
index 385ed8da53c..9b417a410c6 100644
--- a/components/style/values/specified/font.rs
+++ b/components/style/values/specified/font.rs
@@ -794,10 +794,11 @@ impl Parse for FontSizeAdjust {
             let basis = match_ignore_ascii_case! { &ident,
                 "none" => return Ok(FontSizeAdjust::none()),
                 // Check for size adjustment basis keywords if enabled.
-                "ex" if basis_enabled => GenericFontSizeAdjust::Ex,
-                "cap" if basis_enabled => GenericFontSizeAdjust::Cap,
-                "ch" if basis_enabled => GenericFontSizeAdjust::Ch,
-                "ic" if basis_enabled => GenericFontSizeAdjust::Ic,
+                "ex-height" if basis_enabled => GenericFontSizeAdjust::ExHeight,
+                "cap-height" if basis_enabled => GenericFontSizeAdjust::CapHeight,
+                "ch-width" if basis_enabled => GenericFontSizeAdjust::ChWidth,
+                "ic-width" if basis_enabled => GenericFontSizeAdjust::IcWidth,
+                "ic-height" if basis_enabled => GenericFontSizeAdjust::IcHeight,
                 // Unknown (or disabled) keyword.
                 _ => return Err(location.new_custom_error(
                     ::selectors::parser::SelectorParseErrorKind::UnexpectedIdent(ident)
@@ -806,9 +807,9 @@ impl Parse for FontSizeAdjust {
             let value = NonNegativeNumber::parse(context, input)?;
             return Ok(FontSizeAdjust::Value(basis(value)));
         }
-        // Without a basis keyword, the number refers to the 'ex' metric.
+        // Without a basis keyword, the number refers to the 'ex-height' metric.
         let value = NonNegativeNumber::parse(context, input)?;
-        Ok(FontSizeAdjust::Value(GenericFontSizeAdjust::Ex(value)))
+        Ok(FontSizeAdjust::Value(GenericFontSizeAdjust::ExHeight(value)))
     }
 }