diff --git a/src/js/scrollLocks.js b/src/js/scrollLocks.js
index 93602134..b3cf8b79 100644
--- a/src/js/scrollLocks.js
+++ b/src/js/scrollLocks.js
@@ -51,18 +51,17 @@ function lockScroll(container) {
     header,
     main,
     scrollY,
-    lockedMainTop: main ? main.getBoundingClientRect().top : null,
   };
 }
 
 function unlockScroll(
-  { header, main, scrollY, lockedMainTop },
+  { header, main, scrollY },
   { restoreScroll = true } = {},
 ) {
-  let scrollTo = 0;
+  // Not measured at lock time: iOS WebKit can report main's rect there
+  // against the pre-lock scroll offset
+  const releasedMainTop = main ? main.getBoundingClientRect().top : null;
   if (main) {
-    // Follows main if it moved while locked
-    scrollTo = scrollY + lockedMainTop - main.getBoundingClientRect().top;
     main.style.marginTop = "";
     main.style.display = "";
   }
@@ -79,6 +78,12 @@ function unlockScroll(
   body.style.width = "";
   body.style.height = "";
   if (restoreScroll) {
+    let scrollTo = scrollY;
+    if (main) {
+      // Keeps main where it is on screen, following it if it moved while locked
+      const mainDocumentTop = main.getBoundingClientRect().top + window.scrollY;
+      scrollTo = mainDocumentTop - releasedMainTop;
+    }
     window.scrollTo(0, scrollTo);
   }
   resyncIOSFixedLayers();
diff --git a/tests/unit/specs/scrollLock.test.js b/tests/unit/specs/scrollLock.test.js
index d12c6aae..43fcbb30 100644
--- a/tests/unit/specs/scrollLock.test.js
+++ b/tests/unit/specs/scrollLock.test.js
@@ -165,14 +165,47 @@ describe("ScrollLock", () => {
       assert.deepEqual(scrollToCalls[0], [0, 3600]);
     });
 
+    // Locked, main sits where its margin puts it; unlocked, its rect follows
+    // its document position and the scroll position
+    const mockMainRect = (main, layout) => {
+      main.getBoundingClientRect = () => ({
+        top: main.style.marginTop
+          ? layout.lockedTop
+          : layout.documentTop - window.scrollY,
+      });
+    };
+
     it("follows main if it moved while locked", () => {
       const main = container.querySelector("main");
-      main.getBoundingClientRect = () => ({ top: -3500 });
+      const layout = { lockedTop: -3500, documentTop: 100 };
+      mockMainRect(main, layout);
       const lock = createLock();
-      main.getBoundingClientRect = () => ({ top: -3540 });
+      layout.lockedTop = -3540;
       lock.release();
       assert.deepEqual(scrollToCalls[0], [0, 3640]);
     });
+
+    it("ignores a stale lock-time rect (iOS WebKit)", () => {
+      const main = container.querySelector("main");
+      // Seen on iOS: right after locking, the rect is still offset by scrollY
+      main.getBoundingClientRect = () => ({ top: 100 });
+      const lock = createLock();
+      mockMainRect(main, { lockedTop: -3500, documentTop: 100 });
+      lock.release();
+      assert.deepEqual(scrollToCalls[0], [0, 3600]);
+    });
+
+    it("keeps main in place when content above it changed while locked", () => {
+      const main = container.querySelector("main");
+      const layout = { lockedTop: -3500, documentTop: 100 };
+      mockMainRect(main, layout);
+      const lock = createLock();
+      // 300px inserted above main
+      layout.lockedTop = -3200;
+      layout.documentTop = 400;
+      lock.release();
+      assert.deepEqual(scrollToCalls[0], [0, 3600]);
+    });
   });
 
   it("restores a locked scrollable ancestor's overflow on unlock", () => {