diff --git a/scripts/profile_sync.py b/scripts/profile_sync.py
index b91627d1..802cadd7 100644
--- a/scripts/profile_sync.py
+++ b/scripts/profile_sync.py
@@ -488,9 +488,17 @@ def _find_all(haystack: list[str], needle: list[str]) -> list[int]:
 def _map_index(
     opcodes: list[tuple[str, int, int, int, int]], index: int
 ) -> int | None:
+    """Line of HEAD that a pinned line became.
+
+    A replace block of equal size edits each line in place (a column added to
+    every row of a table), so its lines map one to one like an equal block.
+    Collapsed onto the first line, eight refs citing eight rows all landed on
+    the first row.
+    """
     for tag, i1, i2, j1, j2 in opcodes:
         if i1 <= index < i2:
-            return j1 + (index - i1) if tag == "equal" else j1
+            in_place = tag == "equal" or (tag == "replace" and i2 - i1 == j2 - j1)
+            return j1 + (index - i1) if in_place else j1
     return None
 
 
diff --git a/tests/test_profile_sync.py b/tests/test_profile_sync.py
index dd69ddb3..576796db 100644
--- a/tests/test_profile_sync.py
+++ b/tests/test_profile_sync.py
@@ -378,6 +378,15 @@ class TestAnchorBlock(unittest.TestCase):
         self.assertEqual(result.status, "CHANGED")
         self.assertEqual(result.start, 3)
 
+    def test_rows_edited_in_place_keep_their_own_line(self):
+        rows = [f'{{"ipl{i}", 0x{i:02x}}}' for i in range(8)]
+        pin = ["a", "b", *rows, "z"]
+        head = ["a", "b", *[row + ", false" for row in rows], "z"]
+        for line in (3, 5, 10):
+            result = anchor_block(pin, head, line, line)
+            self.assertEqual(result.status, "CHANGED")
+            self.assertEqual(result.start, line)
+
     def test_gone_when_content_vanished(self):
         result = anchor_block(["a", "unique marker", "b"], ["x"] * 200, 2, 2)
         self.assertEqual(result.status, "GONE")