diff --git a/Tests/LibWeb/Text/expected/selection-extend-across-siblings.txt b/Tests/LibWeb/Text/expected/selection-extend-across-siblings.txt
new file mode 100644
index 00000000000..7ef22e9a431
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/selection-extend-across-siblings.txt
@@ -0,0 +1 @@
+PASS
diff --git a/Tests/LibWeb/Text/expected/selection-extend-backwards.txt b/Tests/LibWeb/Text/expected/selection-extend-backwards.txt
new file mode 100644
index 00000000000..7ef22e9a431
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/selection-extend-backwards.txt
@@ -0,0 +1 @@
+PASS
diff --git a/Tests/LibWeb/Text/input/selection-extend-across-siblings.html b/Tests/LibWeb/Text/input/selection-extend-across-siblings.html
new file mode 100644
index 00000000000..dc61ee321b3
--- /dev/null
+++ b/Tests/LibWeb/Text/input/selection-extend-across-siblings.html
@@ -0,0 +1,22 @@
+<script src="include.js"></script>
+<p id="p1">Well hello</p>
+<p id="p2">friends</p>
+
+<script>
+    test(() => {
+        var selection = window.getSelection();
+        selection.setBaseAndExtent(p1.firstChild, 0, p1.firstChild, 0);
+        selection.extend(p2.firstChild, 4);
+        if (selection.anchorNode !== p1.firstChild
+            || selection.anchorOffset !== 0) {
+            println('FAIL: anchor has moved');
+            return;
+        }
+        if (selection.focusNode !== p2.firstChild
+            || selection.focusOffset !== 4) {
+            println('FAIL: focus is not where we expected');
+            return;
+        }
+        println('PASS');
+    })
+</script>
diff --git a/Tests/LibWeb/Text/input/selection-extend-backwards.html b/Tests/LibWeb/Text/input/selection-extend-backwards.html
new file mode 100644
index 00000000000..02722e311a0
--- /dev/null
+++ b/Tests/LibWeb/Text/input/selection-extend-backwards.html
@@ -0,0 +1,21 @@
+<script src="include.js"></script>
+<p id="a">Uno</p>
+
+<script>
+    test(() => {
+        var selection = window.getSelection();
+        selection.setBaseAndExtent(a.firstChild, 3, a.firstChild, 3);
+        selection.extend(a.firstChild, 0);
+        if (selection.anchorNode !== a.firstChild
+            || selection.anchorOffset !== 3) {
+            println('FAIL: anchor has moved');
+            return;
+        }
+        if (selection.focusNode !== a.firstChild
+            || selection.focusOffset !== 0) {
+            println('FAIL: focus is not where we expected');
+            return;
+        }
+        println('PASS');
+    })
+</script>
diff --git a/Userland/Libraries/LibWeb/Selection/Selection.cpp b/Userland/Libraries/LibWeb/Selection/Selection.cpp
index d910b2e1b11..2223a4789aa 100644
--- a/Userland/Libraries/LibWeb/Selection/Selection.cpp
+++ b/Userland/Libraries/LibWeb/Selection/Selection.cpp
@@ -290,7 +290,7 @@ WebIDL::ExceptionOr<void> Selection::extend(JS::NonnullGCPtr<DOM::Node> node, un
         TRY(new_range->set_end(new_focus_node, new_focus_offset));
     }
     // 6. Otherwise, if oldAnchor is before or equal to newFocus, set the start newRange's start to oldAnchor, then set its end to newFocus.
-    else if (old_anchor_node.is_before(new_focus_node) || &old_anchor_node == new_focus_node.ptr()) {
+    else if (position_of_boundary_point_relative_to_other_boundary_point(old_anchor_node, old_anchor_offset, new_focus_node, new_focus_offset) != DOM::RelativeBoundaryPointPosition::After) {
         TRY(new_range->set_start(old_anchor_node, old_anchor_offset));
         TRY(new_range->set_end(new_focus_node, new_focus_offset));
     }
@@ -304,7 +304,7 @@ WebIDL::ExceptionOr<void> Selection::extend(JS::NonnullGCPtr<DOM::Node> node, un
     set_range(new_range);
 
     // 9. If newFocus is before oldAnchor, set this's direction to backwards. Otherwise, set it to forwards.
-    if (new_focus_node->is_before(old_anchor_node)) {
+    if (position_of_boundary_point_relative_to_other_boundary_point(new_focus_node, new_focus_offset, old_anchor_node, old_anchor_offset) == DOM::RelativeBoundaryPointPosition::Before) {
         m_direction = Direction::Backwards;
     } else {
         m_direction = Direction::Forwards;