diff --git a/source/layout/box.cpp b/source/layout/box.cpp
index 14fea3d..8425805 100644
--- a/source/layout/box.cpp
+++ b/source/layout/box.cpp
@@ -183,7 +183,7 @@ BlockFlowBox* Box::createAnonymousBlock(const BoxStyle* parentStyle)
 
 bool Box::canContainFixedPositionedBoxes() const
 {
-    return (hasTransform() && isBlockBox()) || !parentBox();
+    return (hasTransform() && isBlockBox()) || !parentBox() || isRunning();
 }
 
 bool Box::canContainAbsolutePositionedBoxes() const
diff --git a/source/layout/box.h b/source/layout/box.h
index 4bb63e9..e4efd03 100644
--- a/source/layout/box.h
+++ b/source/layout/box.h
@@ -151,6 +151,7 @@ class Box : public HeapMember {
     bool isPositioned() const { return m_isPositioned; }
     bool isFloatingOrPositioned() const { return m_isFloating || m_isPositioned; }
     bool isReplaced() const { return m_isReplaced; }
+    bool isRunning() const { return m_isRunning; }
     bool isOverflowHidden() const { return m_isOverflowHidden; }
     bool isBackgroundStolen() const { return m_isBackgroundStolen; }
     bool isColumnSpanner() const { return m_isColumnSpanner; }
@@ -162,6 +163,7 @@ class Box : public HeapMember {
     void setIsFloating(bool value) { m_isFloating = value; }
     void setIsPositioned(bool value) { m_isPositioned = value; }
     void setIsReplaced(bool value) { m_isReplaced = value; }
+    void setIsRunning(bool value) { m_isRunning = value; }
     void setIsOverflowHidden(bool value) { m_isOverflowHidden = value; }
     void setIsBackgroundStolen(bool value) { m_isBackgroundStolen = value; }
     void setIsColumnSpanner(bool value) { m_isColumnSpanner = value; }
@@ -209,6 +211,7 @@ class Box : public HeapMember {
     bool m_isFloating : 1 {false};
     bool m_isPositioned : 1 {false};
     bool m_isReplaced : 1 {false};
+    bool m_isRunning : 1 {false};
     bool m_isOverflowHidden : 1 {false};
     bool m_isBackgroundStolen : 1 {false};
     bool m_isColumnSpanner : 1 {false};
diff --git a/source/layout/contentbox.cpp b/source/layout/contentbox.cpp
index a39ca16..86b275c 100644
--- a/source/layout/contentbox.cpp
+++ b/source/layout/contentbox.cpp
@@ -108,6 +108,7 @@ void ContentBoxBuilder::addElement(const CSSValue& value)
         return;
     m_box->addChild(newBox);
     element.buildElementBox(m_counters, newBox);
+    newBox->setIsRunning(true);
     m_lastTextBox = nullptr;
 }