diff --git a/components/style/properties/cascade.rs b/components/style/properties/cascade.rs
index 1368cf9c8e7..91d6c6c99dd 100644
--- a/components/style/properties/cascade.rs
+++ b/components/style/properties/cascade.rs
@@ -807,6 +807,7 @@ impl<'a, 'b: 'a> Cascade<'a, 'b> {
             builder.add_flags(ComputedValueFlags::HAS_AUTHOR_SPECIFIED_WORD_SPACING);
         }
 
+        #[cfg(feature = "gecko")]
         if self
             .author_specified
             .contains(LonghandId::FontSynthesis)