diff --git a/ydb/core/tx/schemeshard/schemeshard__operation_alter_pq.cpp b/ydb/core/tx/schemeshard/schemeshard__operation_alter_pq.cpp
index 07be59c52872..e5fcbab7a8e9 100644
--- a/ydb/core/tx/schemeshard/schemeshard__operation_alter_pq.cpp
+++ b/ydb/core/tx/schemeshard/schemeshard__operation_alter_pq.cpp
@@ -792,11 +792,13 @@ class TAlterPQ: public TSubOperation {
             return result;
         }
 
+        const auto& stats = topic->Stats;
         const PQGroupReserve reserve(newTabletConfig, alterData->ActivePartitionCount);
         const PQGroupReserve reserveForCheckLimit(newTabletConfig, alterData->ActivePartitionCount + involvedPartitions.size());
         const PQGroupReserve oldReserve(tabletConfig, topic->ActivePartitionCount);
+        const PQGroupReserve oldReserveForCheckLimit(tabletConfig, topic->ActivePartitionCount, stats.DataSize);
 
-        const ui64 storageToReserve = reserveForCheckLimit.Storage > oldReserve.Storage ? reserveForCheckLimit.Storage - oldReserve.Storage : 0;
+        const ui64 storageToReserve = reserveForCheckLimit.Storage > oldReserveForCheckLimit.Storage ? reserveForCheckLimit.Storage - oldReserveForCheckLimit.Storage : 0;
 
         {
             TPath::TChecker checks = path.Check();
diff --git a/ydb/core/tx/schemeshard/schemeshard_utils.cpp b/ydb/core/tx/schemeshard/schemeshard_utils.cpp
index d6502afbab93..8d5d3f68b606 100644
--- a/ydb/core/tx/schemeshard/schemeshard_utils.cpp
+++ b/ydb/core/tx/schemeshard/schemeshard_utils.cpp
@@ -8,8 +8,9 @@
 namespace NKikimr {
 namespace NSchemeShard {
 
-PQGroupReserve::PQGroupReserve(const ::NKikimrPQ::TPQTabletConfig& tabletConfig, ui64 partitions) {
-    Storage = partitions * NPQ::TopicPartitionReserveSize(tabletConfig);
+PQGroupReserve::PQGroupReserve(const ::NKikimrPQ::TPQTabletConfig& tabletConfig, ui64 partitions, ui64 currentStorageUsage) {
+    Storage = NKikimrPQ::TPQTabletConfig::METERING_MODE_REQUEST_UNITS == tabletConfig.GetMeteringMode()
+        ? currentStorageUsage : partitions * NPQ::TopicPartitionReserveSize(tabletConfig);
     Throughput = partitions * NPQ::TopicPartitionReserveThroughput(tabletConfig);
 }
 
diff --git a/ydb/core/tx/schemeshard/schemeshard_utils.h b/ydb/core/tx/schemeshard/schemeshard_utils.h
index 729764c61e41..3283610ba03f 100644
--- a/ydb/core/tx/schemeshard/schemeshard_utils.h
+++ b/ydb/core/tx/schemeshard/schemeshard_utils.h
@@ -38,7 +38,7 @@ inline NKikimrSchemeOp::TModifyScheme TransactionTemplate(const TString& working
 
 class PQGroupReserve {
 public:
-    PQGroupReserve(const ::NKikimrPQ::TPQTabletConfig& tabletConfig, ui64 partitions);
+    PQGroupReserve(const ::NKikimrPQ::TPQTabletConfig& tabletConfig, ui64 partitions, ui64 currentStorageUsage = 0);
 
     ui64 Storage;
     ui64 Throughput;
diff --git a/ydb/core/tx/schemeshard/ut_base/ut_base.cpp b/ydb/core/tx/schemeshard/ut_base/ut_base.cpp
index 79651dfa906f..3ee4372e24cf 100644
--- a/ydb/core/tx/schemeshard/ut_base/ut_base.cpp
+++ b/ydb/core/tx/schemeshard/ut_base/ut_base.cpp
@@ -11595,6 +11595,88 @@ Y_UNIT_TEST_SUITE(TSchemeShardTest) {
         env.TestWaitNotification(runtime, txId);
     }
 
+    Y_UNIT_TEST(AlterTopicOverDiskSpaceQuotas) {
+        TTestBasicRuntime runtime;
+
+        TTestEnvOptions opts;
+        opts.DisableStatsBatching(true);
+        opts.EnablePersistentPartitionStats(true);
+        opts.EnableTopicDiskSubDomainQuota(true);
+
+        TTestEnv env(runtime, opts);
+
+        ui64 txId = 100;
+
+        // Subdomain with a 1-byte data size quota
+        TestCreateSubDomain(runtime, ++txId,  "/MyRoot", R"(
+                        Name: "USER_1"
+                        PlanResolution: 50
+                        Coordinators: 1
+                        Mediators: 1
+                        TimeCastBucketsPerMediator: 2
+                        StoragePools {
+                            Name: "name_USER_0_kind_hdd-1"
+                            Kind: "hdd-1"
+                        }
+                        StoragePools {
+                            Name: "name_USER_0_kind_hdd-2"
+                            Kind: "hdd-2"
+                        }
+                        DatabaseQuotas {
+                            data_size_hard_quota: 100
+                        }
+                )");
+        env.TestWaitNotification(runtime, txId);
+
+        TestCreatePQGroup(runtime, ++txId, "/MyRoot/USER_1", R"(
+            Name: "Topic1"
+            TotalGroupCount: 1
+            PartitionPerTablet: 1
+            PQTabletConfig {
+                PartitionConfig {
+                    LifetimeSeconds: 1
+                    WriteSpeedInBytesPerSecond : 100
+                }
+                MeteringMode: METERING_MODE_REQUEST_UNITS
+            }
+        )");
+        env.TestWaitNotification(runtime, txId);
+
+        ui64 topicId = DescribePath(runtime, "/MyRoot/USER_1/Topic1").GetPathDescription().GetSelf().GetPathId();
+
+        ui64 generation = 1;
+        ui64 round = 1;
+
+        // Now topic use 50 bytes of the storage
+        SendTEvPeriodicTopicStats(runtime, topicId, generation, ++round, 50, 0);
+
+        // Now we reserve 150 bytes but limit 100 bytes
+        TestAlterPQGroup(runtime, ++txId, "/MyRoot/USER_1", R"(
+            Name: "Topic1"
+            PQTabletConfig {
+                PartitionConfig {
+                    LifetimeSeconds: 1
+                    WriteSpeedInBytesPerSecond : 150
+                }
+                MeteringMode: METERING_MODE_RESERVED_CAPACITY
+            }
+        )", {{TEvSchemeShard::EStatus::StatusResourceExhausted, "database size limit exceeded"}});
+        env.TestWaitNotification(runtime, txId);
+
+        // Now we reserve 100 bytes and limit 100 bytes
+        TestAlterPQGroup(runtime, ++txId, "/MyRoot/USER_1", R"(
+            Name: "Topic1"
+            PQTabletConfig {
+                PartitionConfig {
+                    LifetimeSeconds: 1
+                    WriteSpeedInBytesPerSecond : 100
+                }
+                MeteringMode: METERING_MODE_RESERVED_CAPACITY
+            }
+        )");
+        env.TestWaitNotification(runtime, txId);
+    }
+
     Y_UNIT_TEST(CreateSystemColumn) {
         TTestBasicRuntime runtime;
         TTestEnv env(runtime);