--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
@@ -1120,7 +1121,7 @@ Status WiredTigerUtil::exportTableToBSON(WT_SESSION* session,
     invariant(c);
     ON_BLOCK_EXIT([&] { c->close(c); });

-    std::map<string, BSONObjBuilder*> subs;
+    StringMap<BSONObjBuilder*> subs;
     const char* desc;
     uint64_t value;
     while (c->next(c) == 0 && c->get_value(c, &desc, nullptr, &value) == 0) {
@@ -1155,18 +1156,17 @@ Status WiredTigerUtil::exportTableToBSON(WT_SESSION* session,
                 continue;
             }

-            BSONObjBuilder*& sub = subs[prefix.toString()];
+            BSONObjBuilder*& sub = subs[prefix];
             if (!sub)
                 sub = new BSONObjBuilder();
-            sub->appendNumber(str::ltrim(suffix.toString()), v);
+            sub->appendNumber(str::ltrim(suffix), v);
         }
     }

-    for (std::map<string, BSONObjBuilder*>::const_iterator it = subs.begin(); it != subs.end();
-         ++it) {
-        const std::string& s = it->first;
-        bob->append(s, it->second->obj());
-        delete it->second;
+    for (const auto &kvp : subs ) {
+        const std::string& s = kvp.first;
+        bob->append(s, kvp.second->obj());
+        // delete it->second;
     }
     return Status::OK();
 }