diff --git a/.gitea/workflows/test.yml b/.gitea/workflows/test.yml
index d77d0946..2347d6cc 100644
--- a/.gitea/workflows/test.yml
+++ b/.gitea/workflows/test.yml
@@ -532,6 +532,24 @@ jobs:
           echo ""
         done
 
+  test_root_node:
+    runs-on: ubuntu-latest
+    needs: build
+    container: ${{env.TEST_IMAGE}}:${{github.sha}}
+    steps:
+    - name: Run test
+      id: test
+      timeout-minutes: 3
+      run: /root/vitastor/tests/test_root_node.sh
+    - name: Print logs
+      if: always() && steps.test.outcome == 'failure'
+      run: |
+        for i in /root/vitastor/testdata/*.log /root/vitastor/testdata/*.txt; do
+          echo "-------- $i --------"
+          cat $i
+          echo ""
+        done
+
   test_switch_primary:
     runs-on: ubuntu-latest
     needs: build
diff --git a/mon/lp-optimizer.js b/mon/lp-optimizer.js
index e71a552c..63703532 100644
--- a/mon/lp-optimizer.js
+++ b/mon/lp-optimizer.js
@@ -77,7 +77,7 @@ async function optimize_initial({ osd_weights, combinator, pg_count, pg_size = 3
     {
         if (osd !== NO_OSD)
         {
-            let osd_pg_count = osd_weights[osd]/total_weight*pg_effsize*pg_count;
+            let osd_pg_count = (osd_weights[osd]||0)/total_weight*pg_effsize*pg_count;
             lp += pg_per_osd[osd].join(' + ')+' <= '+osd_pg_count+';\n';
         }
     }
@@ -299,7 +299,7 @@ async function optimize_change({ prev_pgs: prev_int_pgs, osd_weights, combinator
             )).join(' + ');
             const rm_osd_pg_count = (prev_pg_per_osd[osd]||[])
                 .reduce((a, [ old_pg_name, space ]) => (a + (all_pgs_hash[old_pg_name] ? space : 0)), 0);
-            const osd_pg_count = osd_weights[osd]*pg_effsize/total_weight*pg_count - rm_osd_pg_count;
+            const osd_pg_count = (osd_weights[osd]||0)*pg_effsize/total_weight*pg_count - rm_osd_pg_count;
             lp += osd_sum + ' <= ' + osd_pg_count + ';\n';
         }
     }
diff --git a/mon/mon.js b/mon/mon.js
index 88488ed3..f28f1607 100644
--- a/mon/mon.js
+++ b/mon/mon.js
@@ -1197,16 +1197,37 @@ class Mon
         {
             return;
         }
-        pool_tree = pool_tree[root_node];
-        const cur = [ ...(pool_tree||{}).children||[] ];
-        for (let i = 0; i < cur.length; i++)
+        let included = [ ...(pool_tree[root_node] || {}).children||[] ];
+        for (let i = 0; i < included.length; i++)
         {
-            if (cur.children)
+            if (included[i].children)
             {
-                cur.splice(i+1, 1, ...cur.children);
+                included.splice(i+1, 0, ...included[i].children);
+            }
+        }
+        let cur = pool_tree[root_node] || {};
+        if (cur)
+        {
+            included.unshift(cur);
+        }
+        while (cur.id)
+        {
+            let parent = cur.parent||'';
+            if (pool_tree[parent])
+            {
+                included.unshift(pool_tree[parent]);
+                pool_tree[parent] = { ...pool_tree[parent], children: [ cur ] };
+                cur = pool_tree[parent];
+            }
+        }
+        included = included.reduce((a, c) => { a[c.id||''] = true; return a; }, {});
+        for (const item in pool_tree)
+        {
+            if (!included[item])
+            {
+                delete pool_tree[item];
             }
         }
-        return cur;
     }
 
     filter_osds_by_tags(orig_tree, tags)
@@ -1336,7 +1357,7 @@ class Mon
         {
             return null;
         }
-        let pool_tree = osd_tree;
+        let pool_tree = { ...osd_tree };
         this.filter_osds_by_root_node(pool_tree, pool_cfg.root_node);
         this.filter_osds_by_tags(pool_tree, pool_cfg.osd_tags);
         this.filter_osds_by_block_layout(
@@ -1364,9 +1385,9 @@ class Mon
             osd_weights: Object.values(pool_tree).filter(item => item.level === 'osd').reduce((a, c) => { a[c.id] = c.size; return a; }, {}),
             combinator: !this.config.use_old_pg_combinator || pool_cfg.level_placement || pool_cfg.raw_placement
                 // new algorithm:
-                ? new RuleCombinator(osd_tree, this.get_pg_rules(pool_id, pool_cfg), pool_cfg.max_osd_combinations)
+                ? new RuleCombinator(pool_tree, this.get_pg_rules(pool_id, pool_cfg), pool_cfg.max_osd_combinations)
                 // old algorithm:
-                : new SimpleCombinator(flatten_tree(osd_tree[''].children, levels, pool_cfg.failure_domain, 'osd'), pool_cfg.pg_size, pool_cfg.max_osd_combinations),
+                : new SimpleCombinator(flatten_tree(pool_tree[''].children, levels, pool_cfg.failure_domain, 'osd'), pool_cfg.pg_size, pool_cfg.max_osd_combinations),
             pg_count: pool_cfg.pg_count,
             pg_size: pool_cfg.pg_size,
             pg_minsize: pool_cfg.pg_minsize,
diff --git a/tests/run_tests.sh b/tests/run_tests.sh
index 36775989..f44fe279 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -45,6 +45,8 @@ IMMEDIATE_COMMIT=1 ./test_rebalance_verify.sh
 SCHEME=ec ./test_rebalance_verify.sh
 SCHEME=ec IMMEDIATE_COMMIT=1 ./test_rebalance_verify.sh
 
+./test_root_node.sh
+
 ./test_switch_primary.sh
 
 ./test_write.sh
diff --git a/tests/test_root_node.sh b/tests/test_root_node.sh
new file mode 100755
index 00000000..c6538276
--- /dev/null
+++ b/tests/test_root_node.sh
@@ -0,0 +1,31 @@
+#!/bin/bash -ex
+
+. `dirname $0`/common.sh
+
+TIME=$(date '+%s')
+$ETCDCTL put /vitastor/config/global '{"placement_levels":{"rack":100,"host":101,"osd":102}}'
+$ETCDCTL put /vitastor/config/node_placement '{"rack1":{"level":"rack"},"rack2":{"level":"rack"},"stor1":{"level":"host","parent":"rack1"},"stor2":{"level":"host","parent":"rack1"},"stor3":{"level":"host","parent":"rack2"},"stor4":{"level":"host","parent":"rack2"}}'
+$ETCDCTL put /vitastor/osd/stats/1 '{"host":"stor1","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/osd/stats/2 '{"host":"stor1","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/osd/stats/3 '{"host":"stor2","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/osd/stats/4 '{"host":"stor2","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/osd/stats/5 '{"host":"stor3","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/osd/stats/6 '{"host":"stor3","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/osd/stats/7 '{"host":"stor4","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/osd/stats/8 '{"host":"stor4","size":1073741824,"time":"'$TIME'"}'
+$ETCDCTL put /vitastor/config/pools '{"1":{"name":"testpool","scheme":"replicated","pg_size":2,"pg_minsize":2,"pg_count":16,"failure_domain":"host","root_node":"rack1"}}'
+
+node mon/mon-main.js --etcd_address $ETCD_URL --etcd_prefix "/vitastor" >>./testdata/mon.log 2>&1 &
+MON_PID=$!
+
+sleep 2
+
+etcdctl --endpoints=http://localhost:12379 get --prefix /vitastor/config/pgs --print-value-only
+
+if ! (etcdctl --endpoints=http://localhost:12379 get --prefix /vitastor/config/pgs --print-value-only | \
+    jq -s -e '[ [ .[0].items["1"] | .[].osd_set | map(. | select(. != "" and (.|tonumber) < 5)) ][] | select((. | length) == 2) ] | length == 16'); then
+    format_error "Some PGs missing replicas"
+fi
+    format_error "Some PGs missing replicas"
+
+format_green OK