diff --git a/e2e/overviewLane.spec.ts b/e2e/overviewLane.spec.ts
index 6c51df7c..af634991 100644
--- a/e2e/overviewLane.spec.ts
+++ b/e2e/overviewLane.spec.ts
@@ -28,3 +28,22 @@ test("the scrollbar thumb drags even where overview marks cover it (#752)", asyn
   await page.mouse.move(x, box.y + box.height - 20);
   await expect(editor.locator(".cm-openidea-overview")).not.toHaveClass(/cm-openidea-overview-onThumb/);
 });
+
+test("the scrollbar thumb shows over a mark the height of the lane (#1014)", async ({ workbench: page }) => {
+  const editor = await openFromTree(page, "build.gradle.kts");
+  await editor.locator(".cm-content").click();
+  await page.keyboard.press("Meta+a");
+  await page.keyboard.insertText(Array.from({ length: 400 }, (_, i) => `val mark${i} = ${i}`).join("\n"));
+  await page.keyboard.press("Meta+f");
+  await page.getByRole("textbox", { name: "Find" }).fill("mark");
+  await expect(editor.locator(".cm-openidea-overviewMark").first()).toBeVisible();
+  const thumb = editor.locator(".cm-openidea-overviewThumb");
+  await expect(thumb).toBeVisible();
+  // Drawn last in the lane, so it paints over every mark.
+  expect(await thumb.evaluate((t) => t.nextElementSibling)).toBeNull();
+  const scroller = editor.locator(".cm-scroller");
+  const top = async () => (await thumb.boundingBox())!.y;
+  const before = await top();
+  await scroller.evaluate((s) => (s.scrollTop = s.scrollHeight));
+  await expect.poll(top).toBeGreaterThan(before + 100);
+});
diff --git a/src/editor/core/cm/lanes.ts b/src/editor/core/cm/lanes.ts
index 9e6ac7c6..68a2e6c3 100644
--- a/src/editor/core/cm/lanes.ts
+++ b/src/editor/core/cm/lanes.ts
@@ -64,11 +64,18 @@ class OverviewLane {
   private lastKey = "";
   /** The last pointer position over the editor, to re-check the thumb when it scrolls. */
   private pointer: { x: number; y: number } | null = null;
+  /**
+   * The scrollbar thumb drawn over the marks: the native one sits under the lane, so a mark
+   * the height of the lane (a new file) would hide it (#1014).
+   */
+  private thumb: HTMLElement;
 
   constructor(private view: EditorView) {
     this.dom = document.createElement("div");
     this.dom.className = "cm-openidea-overview";
     this.dom.setAttribute("aria-hidden", "true");
+    this.thumb = document.createElement("div");
+    this.thumb.className = "cm-openidea-overviewThumb";
     this.dom.addEventListener("mousedown", this.onMouseDown);
     view.dom.addEventListener("mousemove", this.onPointerMove);
     view.dom.addEventListener("mouseleave", this.onPointerLeave);
@@ -153,9 +160,31 @@ class OverviewLane {
         c.className = "cm-openidea-overviewCaret";
         c.style.top = `${caret}${unit}`;
         frag.appendChild(c);
+        frag.appendChild(this.thumb);
         this.dom.replaceChildren(frag);
       },
     });
+    this.scheduleThumb();
+  }
+
+  private scheduleThumb() {
+    this.view.requestMeasure({
+      key: this.thumb,
+      read: (view) => {
+        const s = view.scrollDOM;
+        const thumb = scrollbarThumb(s.scrollTop, s.scrollHeight, s.clientHeight);
+        // The lane starts at the top of the editor, the scrollbar at the top of the scroller.
+        const offset = s.getBoundingClientRect().top - this.dom.getBoundingClientRect().top;
+        // Inset by the thumb's 2px transparent border (global.css).
+        return thumb && { top: thumb.top + offset + 2, height: thumb.bottom - thumb.top - 4 };
+      },
+      write: (thumb) => {
+        this.thumb.style.display = thumb ? "" : "none";
+        if (!thumb) return;
+        this.thumb.style.top = `${thumb.top}px`;
+        this.thumb.style.height = `${thumb.height}px`;
+      },
+    });
   }
 
   /**
@@ -187,6 +216,7 @@ class OverviewLane {
   };
 
   private onScroll = () => {
+    this.scheduleThumb();
     if (this.pointer) this.updateThumbPassThrough();
   };
 
@@ -218,4 +248,7 @@ class OverviewLane {
   }
 }
 
-export const overviewLane: Extension = ViewPlugin.fromClass(OverviewLane);
+export const overviewLane: Extension = [
+  ViewPlugin.fromClass(OverviewLane),
+  EditorView.editorAttributes.of({ class: "cm-openidea-withOverview" }),
+];
diff --git a/src/editor/core/cm/theme.ts b/src/editor/core/cm/theme.ts
index 3bfd8427..82ce7acc 100644
--- a/src/editor/core/cm/theme.ts
+++ b/src/editor/core/cm/theme.ts
@@ -285,6 +285,17 @@ export const openideaTheme = EditorView.theme({
   ".cm-openidea-overviewMark-thin": { left: "4px", width: "4px", minHeight: "2px" },
   // The scrollbar thumb wins over the marks under it (cm/lanes.ts, #752).
   ".cm-openidea-overview-onThumb .cm-openidea-overviewMark": { pointerEvents: "none" },
+  // The lane draws the thumb over its marks (#1014); the native one only takes the drag.
+  "&.cm-openidea-withOverview .cm-scroller::-webkit-scrollbar-thumb:vertical": { backgroundColor: "transparent" },
+  ".cm-openidea-overviewThumb": {
+    position: "absolute",
+    right: "2px",
+    width: "6px",
+    borderRadius: "3px",
+    background: "var(--scrollbar-thumb)",
+    pointerEvents: "none",
+  },
+  ".cm-openidea-overview-onThumb .cm-openidea-overviewThumb": { background: "var(--scrollbar-thumb-hover)" },
   ".cm-openidea-overviewCaret": {
     position: "absolute",
     left: "2px",