--- a/servo/components/style/properties/longhand/inherited_box.mako.rs
+++ b/servo/components/style/properties/longhand/inherited_box.mako.rs
@@ -14,16 +14,19 @@
                          animation_type="normal",
                          spec="https://drafts.csswg.org/css-box/#propdef-visibility")}
 
 // CSS Writing Modes Level 3
 // https://drafts.csswg.org/css-writing-modes-3
 ${helpers.single_keyword("writing-mode",
                          "horizontal-tb vertical-rl vertical-lr",
                          extra_gecko_values="sideways-rl sideways-lr",
+                         extra_gecko_aliases="lr=horizontal-tb lr-tb=horizontal-tb \
+                                              rl=horizontal-tb rl-tb=horizontal-tb \
+                                              tb=vertical-rl   tb-rl=vertical-rl",
                          experimental=True,
                          need_clone=True,
                          animation_type="none",
                          spec="https://drafts.csswg.org/css-writing-modes/#propdef-writing-mode")}
 
 ${helpers.single_keyword("direction", "ltr rtl", need_clone=True, animation_type="none",
                          spec="https://drafts.csswg.org/css-writing-modes/#propdef-direction",
                          needs_conversion=True)}