diff --git a/components/selectors/context.rs b/components/selectors/context.rs
index 75abfea9f18..f61823a626d 100644
--- a/components/selectors/context.rs
+++ b/components/selectors/context.rs
@@ -127,6 +127,9 @@ where
     /// MatchingContext immutable again.
     nesting_level: usize,
 
+    /// Whether we're inside a negation or not.
+    in_negation: bool,
+
     /// An optional hook function for checking whether a pseudo-element
     /// should match when matching_mode is ForStatelessPseudoElement.
     pub pseudo_element_matching_fn: Option<&'a Fn(&Impl::PseudoElement) -> bool>,
@@ -176,6 +179,7 @@ where
             classes_and_ids_case_sensitivity: quirks_mode.classes_and_ids_case_sensitivity(),
             scope_element: None,
             nesting_level: 0,
+            in_negation: false,
             pseudo_element_matching_fn: None,
             extra_data: Default::default(),
             _impl: ::std::marker::PhantomData,
@@ -188,6 +192,12 @@ where
         self.nesting_level != 0
     }
 
+    /// Whether we're matching inside a :not(..) selector.
+    #[inline]
+    pub fn in_negation(&self) -> bool {
+        self.in_negation
+    }
+
     /// The quirks mode of the document.
     #[inline]
     pub fn quirks_mode(&self) -> QuirksMode {
@@ -212,6 +222,23 @@ where
         result
     }
 
+    /// Runs F with a deeper nesting level, and marking ourselves in a negation,
+    /// for a :not(..) selector, for example.
+    #[inline]
+    pub fn nest_for_negation<F, R>(&mut self, f: F) -> R
+    where
+        F: FnOnce(&mut Self) -> R,
+    {
+        debug_assert!(
+            !self.in_negation,
+            "Someone messed up parsing?"
+        );
+        self.in_negation = true;
+        let result = self.nest(f);
+        self.in_negation = false;
+        result
+    }
+
     #[inline]
     pub fn visited_handling(&self) -> VisitedHandlingMode {
         self.visited_handling
diff --git a/components/selectors/matching.rs b/components/selectors/matching.rs
index 6b1fae8cc32..d52b51d7270 100644
--- a/components/selectors/matching.rs
+++ b/components/selectors/matching.rs
@@ -625,6 +625,8 @@ where
     E: Element,
     F: FnMut(&E, ElementSelectorFlags),
 {
+    debug_assert!(context.shared.is_nested() || !context.shared.in_negation());
+
     match *selector {
         Component::Combinator(_) => unreachable!(),
         Component::Slotted(ref selector) => {
@@ -777,7 +779,7 @@ where
             matches_generic_nth_child(element, context, 0, 1, true, true, flags_setter)
         }
         Component::Negation(ref negated) => {
-            context.shared.nest(|context| {
+            context.shared.nest_for_negation(|context| {
                 let mut local_context = LocalMatchingContext {
                     matches_hover_and_active_quirk: MatchesHoverAndActiveQuirk::No,
                     shared: context,
diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index cdfd8258536..de4855c4ed4 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -2111,7 +2111,7 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
             NonTSPseudoClass::MozWindowInactive => {
                 let state_bit = DocumentState::NS_DOCUMENT_STATE_WINDOW_INACTIVE;
                 if context.extra_data.document_state.intersects(state_bit) {
-                    return true;
+                    return !context.in_negation();
                 }
 
                 self.document_state().contains(state_bit)
@@ -2132,7 +2132,7 @@ impl<'le> ::selectors::Element for GeckoElement<'le> {
                 if context.extra_data.document_state.intersects(state_bit) {
                     // NOTE(emilio): We could still return false for
                     // Direction::Other(..), but we don't bother.
-                    return true;
+                    return !context.in_negation();
                 }
 
                 let doc_is_rtl = self.document_state().contains(state_bit);