diff --git a/src/Storages/MergeTree/MergeTreeIndexVectorSimilarity.cpp b/src/Storages/MergeTree/MergeTreeIndexVectorSimilarity.cpp
index 641770b16e9..bf9aad6545d 100644
--- a/src/Storages/MergeTree/MergeTreeIndexVectorSimilarity.cpp
+++ b/src/Storages/MergeTree/MergeTreeIndexVectorSimilarity.cpp
@@ -5,6 +5,7 @@
 #include <Columns/ColumnArray.h>
 #include <Common/BitHelpers.h>
 #include <Common/formatReadable.h>
+#include <Common/getNumberOfPhysicalCPUCores.h>
 #include <Common/logger_useful.h>
 #include <Common/typeid_cast.h>
 #include <Core/Field.h>
@@ -270,6 +271,8 @@ void updateImpl(const ColumnArray * column_array, const ColumnArray::Offsets & c
 
     /// Reserving space is mandatory
     size_t max_thread_pool_size = Context::getGlobalContextInstance()->getServerSettings().max_build_vector_similarity_index_thread_pool_size;
+    if (max_thread_pool_size == 0)
+        max_thread_pool_size = getNumberOfPhysicalCPUCores();
     unum::usearch::index_limits_t limits(roundUpToPowerOfTwoOrZero(index->size() + rows), max_thread_pool_size);
     index->reserve(limits);