--- a/servo/components/style/properties/longhand/box.mako.rs
+++ b/servo/components/style/properties/longhand/box.mako.rs
@@ -220,20 +220,34 @@
     impl ToComputedValue for SpecifiedValue {
         type ComputedValue = computed_value::T;
 
         #[inline]
         fn to_computed_value(&self, context: &Context) -> computed_value::T {
             let ltr = context.style().writing_mode.is_bidi_ltr();
             // https://drafts.csswg.org/css-logical-props/#float-clear
             match *self {
-                SpecifiedValue::inline_start if ltr => computed_value::T::left,
-                SpecifiedValue::inline_start => computed_value::T::right,
-                SpecifiedValue::inline_end if ltr => computed_value::T::right,
-                SpecifiedValue::inline_end => computed_value::T::left,
+                SpecifiedValue::inline_start => {
+                    context.rule_cache_conditions.borrow_mut()
+                        .set_writing_mode_dependency(context.builder.writing_mode);
+                    if ltr {
+                        computed_value::T::left
+                    } else {
+                        computed_value::T::right
+                    }
+                }
+                SpecifiedValue::inline_end => {
+                    context.rule_cache_conditions.borrow_mut()
+                        .set_writing_mode_dependency(context.builder.writing_mode);
+                    if ltr {
+                        computed_value::T::right
+                    } else {
+                        computed_value::T::left
+                    }
+                }
                 % for value in "none left right".split():
                     SpecifiedValue::${value} => computed_value::T::${value},
                 % endfor
             }
         }
         #[inline]
         fn from_computed_value(computed: &computed_value::T) -> SpecifiedValue {
             match *computed {
@@ -258,20 +272,34 @@
     impl ToComputedValue for SpecifiedValue {
         type ComputedValue = computed_value::T;
 
         #[inline]
         fn to_computed_value(&self, context: &Context) -> computed_value::T {
             let ltr = context.style().writing_mode.is_bidi_ltr();
             // https://drafts.csswg.org/css-logical-props/#float-clear
             match *self {
-                SpecifiedValue::inline_start if ltr => computed_value::T::left,
-                SpecifiedValue::inline_start => computed_value::T::right,
-                SpecifiedValue::inline_end if ltr => computed_value::T::right,
-                SpecifiedValue::inline_end => computed_value::T::left,
+                SpecifiedValue::inline_start => {
+                    context.rule_cache_conditions.borrow_mut()
+                        .set_writing_mode_dependency(context.builder.writing_mode);
+                    if ltr {
+                        computed_value::T::left
+                    } else {
+                        computed_value::T::right
+                    }
+                }
+                SpecifiedValue::inline_end => {
+                    context.rule_cache_conditions.borrow_mut()
+                        .set_writing_mode_dependency(context.builder.writing_mode);
+                    if ltr {
+                        computed_value::T::right
+                    } else {
+                        computed_value::T::left
+                    }
+                }
                 % for value in "none left right both".split():
                     SpecifiedValue::${value} => computed_value::T::${value},
                 % endfor
             }
         }
         #[inline]
         fn from_computed_value(computed: &computed_value::T) -> SpecifiedValue {
             match *computed {