--- a/servo/components/style/properties/gecko.mako.rs
+++ b/servo/components/style/properties/gecko.mako.rs
@@ -615,19 +615,16 @@ impl Debug for ${style_struct.gecko_stru
     force_stub += ["font-variant"]
     # These have unusual representations in gecko.
     force_stub += ["list-style-type"]
 
     # These are part of shorthands so we must include them in stylo builds,
     # but we haven't implemented the stylo glue for the longhand
     # so we generate a stub
     force_stub += ["flex-basis", # position
-
-                   # transition
-                   "transition-property",
                    ]
 
     # Types used with predefined_type()-defined properties that we can auto-generate.
     predefined_types = {
         "length::LengthOrAuto": impl_style_coord,
         "length::LengthOrNormal": impl_style_coord,
         "Length": impl_absolute_length,
         "Position": impl_position,
@@ -1358,16 +1355,20 @@ fn static_assert() {
         self.gecko.m${type.capitalize()}s[index].mTimingFunction.into()
     }
 </%def>
 
 <%def name="impl_transition_time_value(ident, gecko_ffi_name)">
     ${impl_animation_or_transition_time_value('transition', ident, gecko_ffi_name)}
 </%def>
 
+<%def name="impl_transition_count(ident, gecko_ffi_name)">
+    ${impl_animation_or_transition_count('transition', ident, gecko_ffi_name)}
+</%def>
+
 <%def name="impl_copy_animation_value(ident, gecko_ffi_name)">
     ${impl_copy_animation_or_transition_value('animation', ident, gecko_ffi_name)}
 </%def>
 
 <%def name="impl_transition_timing_function()">
     ${impl_animation_or_transition_timing_function('transition')}
 </%def>
 
@@ -1419,17 +1420,17 @@ fn static_assert() {
     ${impl_copy_animation_value(ident, gecko_ffi_name)}
 </%def>
 
 <% skip_box_longhands= """display overflow-y vertical-align
                           animation-name animation-delay animation-duration
                           animation-direction animation-fill-mode animation-play-state
                           animation-iteration-count animation-timing-function
                           transition-duration transition-delay
-                          transition-timing-function
+                          transition-timing-function transition-property
                           page-break-before page-break-after
                           scroll-snap-points-x scroll-snap-points-y transform
                           scroll-snap-type-y scroll-snap-coordinate
                           perspective-origin transform-origin""" %>
 <%self:impl_trait style_struct_name="Box" skip_longhands="${skip_box_longhands}">
 
     // We manually-implement the |display| property until we get general
     // infrastructure for preffing certain values.
@@ -1767,16 +1768,48 @@ fn static_assert() {
         }
         computed_value::T(Some(result))
     }
 
     ${impl_transition_time_value('delay', 'Delay')}
     ${impl_transition_time_value('duration', 'Duration')}
     ${impl_transition_timing_function()}
 
+    pub fn set_transition_property(&mut self, v: longhands::transition_property::computed_value::T) {
+        use gecko_bindings::structs::nsCSSPropertyID_eCSSPropertyExtra_no_properties;
+
+        unsafe { self.gecko.mTransitions.ensure_len(v.0.len()) };
+        if !v.0.is_empty() {
+            self.gecko.mTransitionPropertyCount = v.0.len() as u32;
+            for (servo, gecko) in v.0.into_iter().zip(self.gecko.mTransitions.iter_mut()) {
+                gecko.mProperty = servo.into();
+            }
+        } else {
+            // In gecko |none| is represented by eCSSPropertyExtra_no_properties.
+            self.gecko.mTransitionPropertyCount = 1;
+            self.gecko.mTransitions[0].mProperty = nsCSSPropertyID_eCSSPropertyExtra_no_properties;
+        }
+    }
+    pub fn transition_property_at(&self, index: usize)
+        -> longhands::transition_property::computed_value::SingleComputedValue {
+        self.gecko.mTransitions[index].mProperty.into()
+    }
+
+    pub fn copy_transition_property_from(&mut self, other: &Self) {
+        unsafe { self.gecko.mTransitions.ensure_len(other.gecko.mTransitions.len()) };
+
+        let count = other.gecko.mTransitionPropertyCount;
+        self.gecko.mTransitionPropertyCount = count;
+
+        for (index, transition) in self.gecko.mTransitions.iter_mut().enumerate().take(count as usize) {
+            transition.mProperty = other.gecko.mTransitions[index].mProperty;
+        }
+    }
+    ${impl_transition_count('property', 'Property')}
+
     pub fn set_animation_name(&mut self, v: longhands::animation_name::computed_value::T) {
         use nsstring::nsCString;
         unsafe { self.gecko.mAnimations.ensure_len(v.0.len()) };
 
         if v.0.len() > 0 {
             self.gecko.mAnimationNameCount = v.0.len() as u32;
             for (servo, gecko) in v.0.into_iter().zip(self.gecko.mAnimations.iter_mut()) {
                 gecko.mName.assign_utf8(&nsCString::from(servo.0.to_string()));

--- a/servo/components/style/properties/helpers/animated_properties.mako.rs
+++ b/servo/components/style/properties/helpers/animated_properties.mako.rs
@@ -121,16 +121,34 @@ impl From<TransitionProperty> for nsCSSP
                         => ${helpers.to_nscsspropertyid(prop.ident)},
                 % endif
             % endfor
             TransitionProperty::All => nsCSSPropertyID::eCSSPropertyExtra_all_properties,
         }
     }
 }
 
+/// Convert nsCSSPropertyID to TransitionProperty
+#[cfg(feature = "gecko")]
+#[allow(non_upper_case_globals)]
+impl From<nsCSSPropertyID> for TransitionProperty {
+    fn from(property: nsCSSPropertyID) -> TransitionProperty {
+        match property {
+            % for prop in data.longhands:
+                % if prop.animatable:
+                    ${helpers.to_nscsspropertyid(prop.ident)}
+                        => TransitionProperty::${prop.camel_case},
+                % endif
+            % endfor
+            nsCSSPropertyID::eCSSPropertyExtra_all_properties => TransitionProperty::All,
+            _ => panic!(),
+        }
+    }
+}
+
 /// Convert to PropertyDeclarationId.
 #[cfg(feature = "gecko")]
 #[allow(non_upper_case_globals)]
 impl<'a> From<TransitionProperty> for PropertyDeclarationId<'a> {
     fn from(transition_property: TransitionProperty) -> PropertyDeclarationId<'a> {
         match transition_property {
             % for prop in data.longhands:
                 % if prop.animatable: