diff --git a/components/style/gecko/generated/bindings.rs b/components/style/gecko/generated/bindings.rs
index e8ec71f6615f..e94e1cd96eb1 100644
--- a/components/style/gecko/generated/bindings.rs
+++ b/components/style/gecko/generated/bindings.rs
@@ -11,6 +11,8 @@ use gecko_bindings::structs::mozilla::css::URLValue;
 use gecko_bindings::structs::mozilla::MallocSizeOf;
 use gecko_bindings::structs::mozilla::Side;
 use gecko_bindings::structs::nsIContent;
+use gecko_bindings::structs::nsIDocument;
+use gecko_bindings::structs::nsIDocument_DocumentTheme;
 use gecko_bindings::structs::RawGeckoAnimationPropertySegment;
 use gecko_bindings::structs::RawGeckoComputedTiming;
 use gecko_bindings::structs::RawGeckoCSSPropertyIDList;
@@ -583,6 +585,10 @@ extern "C" {
     pub fn Gecko_GetXMLLangValue(element: RawGeckoElementBorrowed)
      -> *mut nsIAtom;
 }
+extern "C" {
+    pub fn Gecko_GetDocumentLWTheme(aDocument: *const nsIDocument)
+     -> nsIDocument_DocumentTheme;
+}
 extern "C" {
     pub fn Gecko_AtomAttrValue(element: RawGeckoElementBorrowed,
                                attribute: *mut nsIAtom) -> *mut nsIAtom;
diff --git a/components/style/gecko/non_ts_pseudo_class_list.rs b/components/style/gecko/non_ts_pseudo_class_list.rs
index 8beb8c984932..92da05b5b64f 100644
--- a/components/style/gecko/non_ts_pseudo_class_list.rs
+++ b/components/style/gecko/non_ts_pseudo_class_list.rs
@@ -26,7 +26,6 @@
  *
  * Pending pseudo-classes:
  *
- *  :-moz-lwtheme, :-moz-lwtheme-brighttext, :-moz-lwtheme-darktext,
  *  :-moz-window-inactive.
  *
  *  :scope -> <style scoped>, pending discussion.
@@ -114,6 +113,9 @@ macro_rules! apply_non_ts_list {
                 ("-moz-use-shadow-tree-root", MozUseShadowTreeRoot, mozUseShadowTreeRoot, _, PSEUDO_CLASS_INTERNAL),
                 ("-moz-is-html", MozIsHTML, mozIsHTML, _, _),
                 ("-moz-placeholder", MozPlaceholder, mozPlaceholder, _, _),
+                ("-moz-lwtheme", MozLWTheme, mozLWTheme, _, _),
+                ("-moz-lwtheme-brighttext", MozLWThemeBrightText, mozLWThemeBrightText, _, _),
+                ("-moz-lwtheme-darktext", MozLWThemeDarkText, mozLWThemeDarkText, _, _),
             ],
             string: [
                 ("-moz-system-metric", MozSystemMetric, mozSystemMetric, _, PSEUDO_CLASS_INTERNAL),
diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index 9f2169028ca6..cc980fd86d1f 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -31,7 +31,8 @@ use gecko::selector_parser::{SelectorImpl, NonTSPseudoClass, PseudoElement};
 use gecko::snapshot_helpers;
 use gecko_bindings::bindings;
 use gecko_bindings::bindings::{Gecko_DropStyleChildrenIterator, Gecko_MaybeCreateStyleChildrenIterator};
-use gecko_bindings::bindings::{Gecko_ElementState, Gecko_GetLastChild, Gecko_GetNextStyleChild};
+use gecko_bindings::bindings::{Gecko_ElementState, Gecko_GetDocumentLWTheme};
+use gecko_bindings::bindings::{Gecko_GetLastChild, Gecko_GetNextStyleChild};
 use gecko_bindings::bindings::{Gecko_IsRootElement, Gecko_MatchesElement, Gecko_Namespace};
 use gecko_bindings::bindings::{Gecko_SetNodeFlags, Gecko_UnsetNodeFlags};
 use gecko_bindings::bindings::Gecko_ClassOrClassList;
@@ -62,6 +63,7 @@ use gecko_bindings::structs::ELEMENT_HAS_SNAPSHOT;
 use gecko_bindings::structs::EffectCompositor_CascadeLevel as CascadeLevel;
 use gecko_bindings::structs::NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE;
 use gecko_bindings::structs::NODE_IS_NATIVE_ANONYMOUS;
+use gecko_bindings::structs::nsIDocument_DocumentTheme as DocumentTheme;
 use gecko_bindings::sugar::ownership::{HasArcFFI, HasSimpleFFI};
 use logical_geometry::WritingMode;
 use media_queries::Device;
@@ -586,6 +588,12 @@ impl<'le> GeckoElement<'le> {
     fn may_have_style_attribute(&self) -> bool {
         self.as_node().get_bool_flag(nsINode_BooleanFlag::ElementMayHaveStyle)
     }
+
+    #[inline]
+    fn get_document_theme(&self) -> DocumentTheme {
+        let node = self.as_node();
+        unsafe { Gecko_GetDocumentLWTheme(node.owner_doc()) }
+    }
 }
 
 /// Converts flags from the layout used by rust-selectors to the layout used
@@ -1659,6 +1667,15 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
             NonTSPseudoClass::MozIsHTML => {
                 self.is_html_element_in_html_document()
             }
+            NonTSPseudoClass::MozLWTheme => {
+                self.get_document_theme() != DocumentTheme::Doc_Theme_None
+            }
+            NonTSPseudoClass::MozLWThemeBrightText => {
+                self.get_document_theme() == DocumentTheme::Doc_Theme_Bright
+            }
+            NonTSPseudoClass::MozLWThemeDarkText => {
+                self.get_document_theme() == DocumentTheme::Doc_Theme_Dark
+            }
             NonTSPseudoClass::MozPlaceholder => false,
             NonTSPseudoClass::MozAny(ref sels) => {
                 let old_value = context.hover_active_quirk_disabled;