diff --git a/src/app/update/dialog.rs b/src/app/update/dialog.rs
index 403959ecb..fc46feea1 100644
--- a/src/app/update/dialog.rs
+++ b/src/app/update/dialog.rs
@@ -636,6 +636,7 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
             }
             DockMsg::DragMove(point) => {
                 if self.dock_dragging.is_some() {
+                    let avail = self.tabs[self.active_tab].scene.selection.borrow().vp_size.1;
                     let side = if point.x < self.win_size.0 * 0.5 {
                         DockSide::Left
                     } else {
@@ -644,7 +645,7 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                     let index = crate::ui::dock::drop_index(
                         point.y,
                         std::cmp::max(self.dock.len(side), 1),
-                        self.win_size.1,
+                        avail,
                     );
                     self.dock_drag_target = Some((side, index));
                 } else if let Some(id) = self.dock_resizing {
diff --git a/src/app/view/mod.rs b/src/app/view/mod.rs
index 7a5929f8c..fec1d8a81 100644
--- a/src/app/view/mod.rs
+++ b/src/app/view/mod.rs
@@ -1563,7 +1563,8 @@ impl OpenCADStudio {
             } else {
                 self.dock.len(side) + 1
             };
-            let slot_h = self.win_size.1 / final_count as f32;
+            let edge_h = tab.scene.selection.borrow().vp_size.1;
+            let slot_h = edge_h / final_count as f32;
             let index = self.dock_drag_target.map(|(_, i)| i).unwrap_or(0);
             let slot = index.min(final_count.saturating_sub(1));
             let ghost_top = slot as f32 * slot_h;