diff --git a/CHANGES.rst b/CHANGES.rst
index 6cef031159d..b47f417e9a1 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -18,5 +18,8 @@ Features added
 Bugs fixed
 ----------
 
+* #13060: HTML Search: use ``Map`` to store per-file term scores.
+  Patch by James Addison
+
 Testing
 -------
diff --git a/sphinx/themes/basic/static/searchtools.js b/sphinx/themes/basic/static/searchtools.js
index 2c774d17aff..aaf078d2b91 100644
--- a/sphinx/themes/basic/static/searchtools.js
+++ b/sphinx/themes/basic/static/searchtools.js
@@ -547,8 +547,9 @@ const Search = {
 
         // set score for the word in each file
         recordFiles.forEach((file) => {
-          if (!scoreMap.has(file)) scoreMap.set(file, {});
-          scoreMap.get(file)[word] = record.score;
+          if (!scoreMap.has(file)) scoreMap.set(file, new Map());
+          const fileScores = scoreMap.get(file);
+          fileScores.set(word, record.score);
         });
       });
 
@@ -587,7 +588,7 @@ const Search = {
         break;
 
       // select one (max) score for the file.
-      const score = Math.max(...wordList.map((w) => scoreMap.get(file)[w]));
+      const score = Math.max(...wordList.map((w) => scoreMap.get(file).get(w)));
       // add result to the result list
       results.push([
         docNames[file],