diff --git a/Libraries/LibWeb/Rust/src/layout/flex_formatting_context.rs b/Libraries/LibWeb/Rust/src/layout/flex_formatting_context.rs
index ec9a2d0453bce..8f64fc2a5d58e 100644
--- a/Libraries/LibWeb/Rust/src/layout/flex_formatting_context.rs
+++ b/Libraries/LibWeb/Rust/src/layout/flex_formatting_context.rs
@@ -865,13 +865,35 @@ impl<'pass> FlexFormattingContext<'pass> {
     }
 
     fn calculate_min_content_inline_size(&self, index: usize) -> CssPixels {
-        self.sizing()
-            .calculate_min_content_inline_size(self.flex_items[index].box_, self.item_containing_block_constraints())
+        let sizing = self.sizing();
+        let node = self.flex_items[index].box_;
+        let constraints = self.item_containing_block_constraints();
+        let used = self.item_used(index);
+        if used.has_definite_block_size() {
+            sizing.calculate_min_content_inline_size_at_definite_block_size(
+                node,
+                constraints,
+                used.content_block_size.get(),
+            )
+        } else {
+            sizing.calculate_min_content_inline_size(node, constraints)
+        }
     }
 
     fn calculate_max_content_inline_size(&self, index: usize) -> CssPixels {
-        self.sizing()
-            .calculate_max_content_inline_size(self.flex_items[index].box_, self.item_containing_block_constraints())
+        let sizing = self.sizing();
+        let node = self.flex_items[index].box_;
+        let constraints = self.item_containing_block_constraints();
+        let used = self.item_used(index);
+        if used.has_definite_block_size() {
+            sizing.calculate_max_content_inline_size_at_definite_block_size(
+                node,
+                constraints,
+                used.content_block_size.get(),
+            )
+        } else {
+            sizing.calculate_max_content_inline_size(node, constraints)
+        }
     }
 
     fn calculate_min_content_block_size(&self, index: usize, inline_size: CssPixels) -> CssPixels {
diff --git a/Libraries/LibWeb/Rust/src/layout/formatting_context.rs b/Libraries/LibWeb/Rust/src/layout/formatting_context.rs
index 3a257701a3372..44c5464969063 100644
--- a/Libraries/LibWeb/Rust/src/layout/formatting_context.rs
+++ b/Libraries/LibWeb/Rust/src/layout/formatting_context.rs
@@ -203,10 +203,12 @@ impl MeasurementState {
 
 fn cache_key(
     measured_at_inline_size: Option<CssPixels>,
+    measured_at_block_size: Option<CssPixels>,
     constraints: ContainingBlockConstraints,
 ) -> IntrinsicSizeCacheKey {
     IntrinsicSizeCacheKey {
         measured_at_inline_size,
+        measured_at_block_size,
         percentage_basis_inline_size: constraints.percentage_basis_inline_size,
         percentage_basis_block_size: constraints.percentage_basis_block_size,
         quirks_mode_percentage_basis_block_size: constraints.quirks_mode_percentage_basis_block_size,
diff --git a/Libraries/LibWeb/Rust/src/layout/layout_node_arena.rs b/Libraries/LibWeb/Rust/src/layout/layout_node_arena.rs
index b48e97e5085d7..e7fff8a7e34ae 100644
--- a/Libraries/LibWeb/Rust/src/layout/layout_node_arena.rs
+++ b/Libraries/LibWeb/Rust/src/layout/layout_node_arena.rs
@@ -24,6 +24,7 @@ pub(crate) const SLOTS_PER_CHUNK: usize = 256;
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
 pub(crate) struct IntrinsicSizeCacheKey {
     pub(crate) measured_at_inline_size: Option<CssPixels>,
+    pub(crate) measured_at_block_size: Option<CssPixels>,
     pub(crate) percentage_basis_inline_size: Option<CssPixels>,
     pub(crate) percentage_basis_block_size: Option<CssPixels>,
     pub(crate) quirks_mode_percentage_basis_block_size: Option<CssPixels>,
@@ -42,6 +43,7 @@ impl Hash for IntrinsicSizeCacheKey {
         }
 
         hash_optional(self.measured_at_inline_size, state);
+        hash_optional(self.measured_at_block_size, state);
         hash_optional(self.percentage_basis_inline_size, state);
         hash_optional(self.percentage_basis_block_size, state);
         hash_optional(self.quirks_mode_percentage_basis_block_size, state);
diff --git a/Libraries/LibWeb/Rust/src/layout/sizing_context.rs b/Libraries/LibWeb/Rust/src/layout/sizing_context.rs
index c5e17d92bd250..7f8c611a6bec7 100644
--- a/Libraries/LibWeb/Rust/src/layout/sizing_context.rs
+++ b/Libraries/LibWeb/Rust/src/layout/sizing_context.rs
@@ -1169,7 +1169,7 @@ impl SizingContext {
             self.intrinsic_inline_measurement_cache_get(
                 node,
                 IntrinsicSizeCacheKind::MaxContentInline,
-                cache_key(None, constraints),
+                cache_key(None, None, constraints),
             )?
             .min_content_inline_size_from_max_content_layout?
         } else {
@@ -1322,7 +1322,11 @@ impl SizingContext {
             AvailableSize::MaxContent => IntrinsicSizeCacheKind::MaxContentInline,
             AvailableSize::Definite(_) | AvailableSize::Indefinite => return None,
         };
-        let measurement = self.intrinsic_inline_measurement_cache_get(node, kind, cache_key(None, constraints))?;
+        let measurement = self.intrinsic_inline_measurement_cache_get(
+            node,
+            kind,
+            cache_key(None, None, constraints),
+        )?;
         if measurement.available_block_size != available_block_size {
             return None;
         }
@@ -1383,6 +1387,24 @@ impl SizingContext {
         &self,
         node: Node,
         constraints: ContainingBlockConstraints,
+    ) -> CssPixels {
+        self.calculate_min_content_inline_size_with_block_size(node, constraints, None)
+    }
+
+    pub(crate) fn calculate_min_content_inline_size_at_definite_block_size(
+        &self,
+        node: Node,
+        constraints: ContainingBlockConstraints,
+        block_size: CssPixels,
+    ) -> CssPixels {
+        self.calculate_min_content_inline_size_with_block_size(node, constraints, Some(block_size))
+    }
+
+    fn calculate_min_content_inline_size_with_block_size(
+        &self,
+        node: Node,
+        constraints: ContainingBlockConstraints,
+        block_size: Option<CssPixels>,
     ) -> CssPixels {
         let facts = self.facts(node);
         let style = self.style(node);
@@ -1432,25 +1454,26 @@ impl SizingContext {
         if let Some(cached) = self.intrinsic_inline_measurement_cache_get(
             node,
             IntrinsicSizeCacheKind::MinContentInline,
-            cache_key(None, constraints),
+            cache_key(None, block_size, constraints),
         ) {
             return cached.automatic_content_inline_size;
         }
-        if let Some(min_content_inline_size) = self.paired_min_content_inline_size(node, constraints) {
+        if let Some(min_content_inline_size) = self.paired_min_content_inline_size(node, constraints, block_size) {
             return min_content_inline_size;
         }
-        self.measure_intrinsic_inline_size(node, constraints, IntrinsicSizeCacheKind::MinContentInline)
+        self.measure_intrinsic_inline_size(node, constraints, block_size, IntrinsicSizeCacheKind::MinContentInline)
     }
 
     fn paired_min_content_inline_size(
         &self,
         node: Node,
         constraints: ContainingBlockConstraints,
+        block_size: Option<CssPixels>,
     ) -> Option<CssPixels> {
         self.intrinsic_inline_measurement_cache_get(
             node,
             IntrinsicSizeCacheKind::MaxContentInline,
-            cache_key(None, constraints),
+            cache_key(None, block_size, constraints),
         )?
         .min_content_inline_size_from_max_content_layout
     }
@@ -1459,6 +1482,24 @@ impl SizingContext {
         &self,
         node: Node,
         constraints: ContainingBlockConstraints,
+    ) -> CssPixels {
+        self.calculate_max_content_inline_size_with_block_size(node, constraints, None)
+    }
+
+    pub(crate) fn calculate_max_content_inline_size_at_definite_block_size(
+        &self,
+        node: Node,
+        constraints: ContainingBlockConstraints,
+        block_size: CssPixels,
+    ) -> CssPixels {
+        self.calculate_max_content_inline_size_with_block_size(node, constraints, Some(block_size))
+    }
+
+    fn calculate_max_content_inline_size_with_block_size(
+        &self,
+        node: Node,
+        constraints: ContainingBlockConstraints,
+        block_size: Option<CssPixels>,
     ) -> CssPixels {
         let facts = self.facts(node);
         let style = self.style(node);
@@ -1614,7 +1655,7 @@ impl SizingContext {
         if !self.has_children(node) {
             return CssPixels::default();
         }
-        self.measure_intrinsic_inline_size(node, constraints, IntrinsicSizeCacheKind::MaxContentInline)
+        self.measure_intrinsic_inline_size(node, constraints, block_size, IntrinsicSizeCacheKind::MaxContentInline)
     }
 
     // Lays `node` out under an intrinsic inline-size constraint, reusing and populating the measurement cache.
@@ -1622,6 +1663,7 @@ impl SizingContext {
         &self,
         node: Node,
         constraints: ContainingBlockConstraints,
+        block_size: Option<CssPixels>,
         kind: IntrinsicSizeCacheKind,
     ) -> CssPixels {
         let (size_constraint, available_inline_size) = match kind {
@@ -1629,13 +1671,20 @@ impl SizingContext {
             IntrinsicSizeCacheKind::MaxContentInline => (SizeConstraint::MaxContent, AvailableSize::MaxContent),
             _ => unreachable!("inline measurement cache kind must use the inline axis"),
         };
-        let key = cache_key(None, constraints);
+        let key = cache_key(None, block_size, constraints);
         if let Some(cached) = self.intrinsic_inline_measurement_cache_get(node, kind, key) {
             return cached.automatic_content_inline_size;
         }
 
         let measurement = MeasurementState::create(self.callbacks);
         let root = measurement.create_used_values(node, constraints);
+        // NB: A parent layout can assign a definite block size that is not present in computed style,
+        //     such as the stretched cross size of a flex item. Preserve it so descendant percentages
+        //     resolve against the same size during intrinsic measurement.
+        if let Some(block_size) = block_size {
+            root.set_content_block_size(block_size);
+            root.has_definite_block_size.set(true);
+        }
         root.inline_size_constraint.set(size_constraint);
         root.has_definite_inline_size.set(false);
         let block_size = if root.has_definite_block_size() {
@@ -1677,7 +1726,7 @@ impl SizingContext {
             IntrinsicSizeCacheKind::MaxContentBlock => (SizeConstraint::MaxContent, AvailableSize::MaxContent),
             _ => unreachable!("block size cache kind must use the block axis"),
         };
-        let key = cache_key(Some(inline_size), constraints);
+        let key = cache_key(Some(inline_size), None, constraints);
         if let Some(cached) = self.intrinsic_block_cache_get(node, kind, key) {
             return cached;
         }
diff --git a/Tests/LibWeb/Text/expected/flex-item-intrinsic-width-from-aspect-ratio-child.txt b/Tests/LibWeb/Text/expected/flex-item-intrinsic-width-from-aspect-ratio-child.txt
new file mode 100644
index 0000000000000..7437d77eebc7a
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/flex-item-intrinsic-width-from-aspect-ratio-child.txt
@@ -0,0 +1,2 @@
+item width: 400
+child width: 400
diff --git a/Tests/LibWeb/Text/input/flex-item-intrinsic-width-from-aspect-ratio-child.html b/Tests/LibWeb/Text/input/flex-item-intrinsic-width-from-aspect-ratio-child.html
new file mode 100644
index 0000000000000..b3b3e85be7745
--- /dev/null
+++ b/Tests/LibWeb/Text/input/flex-item-intrinsic-width-from-aspect-ratio-child.html
@@ -0,0 +1,33 @@
+<!doctype html>
+<link rel="help" href="https://drafts.csswg.org/css-flexbox-1/#intrinsic-item-contributions">
+<link rel="help" href="https://drafts.csswg.org/css-sizing-4/#aspect-ratio-size-transfers">
+<script src="include.js"></script>
+<style>
+    #container {
+        display: flex;
+        width: 300px;
+        height: 200px;
+    }
+
+    #item {
+        display: flex;
+        flex-shrink: 0;
+    }
+
+    #child {
+        width: auto;
+        height: 100%;
+        aspect-ratio: 2 / 1;
+    }
+</style>
+<div id="container">
+    <div id="item">
+        <div id="child"></div>
+    </div>
+</div>
+<script>
+    test(() => {
+        println(`item width: ${item.getBoundingClientRect().width}`);
+        println(`child width: ${child.getBoundingClientRect().width}`);
+    });
+</script>