diff --git a/lib/mergeset/table.go b/lib/mergeset/table.go
index 158b96cd4c..4d0923981d 100644
--- a/lib/mergeset/table.go
+++ b/lib/mergeset/table.go
@@ -254,6 +254,14 @@ func (ris *rawItemsShard) addItems(tb *Table, items [][]byte) [][]byte {
 
 	tb.flushBlocksToParts(ibsToFlush, false)
 
+	if len(ibsToFlush) > 0 {
+		// Run assisted merges if needed.
+		flushConcurrencyCh <- struct{}{}
+		tb.assistedMergeForInmemoryParts()
+		tb.assistedMergeForFileParts()
+		<-flushConcurrencyCh
+	}
+
 	return tailItems
 }
 
@@ -749,11 +757,6 @@ func (tb *Table) flushBlocksToParts(ibs []*inmemoryBlock, isFinal bool) {
 	tb.inmemoryParts = append(tb.inmemoryParts, pws...)
 	tb.partsLock.Unlock()
 
-	flushConcurrencyCh <- struct{}{}
-	tb.assistedMergeForInmemoryParts()
-	tb.assistedMergeForFileParts()
-	<-flushConcurrencyCh
-
 	if tb.flushCallback != nil {
 		if isFinal {
 			tb.flushCallback()
diff --git a/lib/storage/partition.go b/lib/storage/partition.go
index 65616ee6b6..22815a77d7 100644
--- a/lib/storage/partition.go
+++ b/lib/storage/partition.go
@@ -515,6 +515,14 @@ func (rrs *rawRowsShard) addRows(pt *partition, rows []rawRow) []rawRow {
 	if rrb != nil {
 		pt.flushRowsToParts(rrb.rows)
 		putRawRowsBlock(rrb)
+
+		// Run assisted merges if needed.
+		flushConcurrencyCh <- struct{}{}
+		pt.assistedMergeForInmemoryParts()
+		pt.assistedMergeForSmallParts()
+		// There is no need in assisted merges for big parts,
+		// since the bottleneck is possible only at inmemory and small parts.
+		<-flushConcurrencyCh
 	}
 
 	return rows
@@ -582,13 +590,6 @@ func (pt *partition) flushRowsToParts(rows []rawRow) {
 	pt.partsLock.Lock()
 	pt.inmemoryParts = append(pt.inmemoryParts, pws...)
 	pt.partsLock.Unlock()
-
-	flushConcurrencyCh <- struct{}{}
-	pt.assistedMergeForInmemoryParts()
-	pt.assistedMergeForSmallParts()
-	<-flushConcurrencyCh
-	// There is no need in assisted merges for small and big parts,
-	// since the bottleneck is possible only at inmemory parts.
 }
 
 var flushConcurrencyCh = make(chan struct{}, cgroup.AvailableCPUs())