diff --git a/src/Dictionaries/DictionaryHelpers.h b/src/Dictionaries/DictionaryHelpers.h
index 04828d4d76f..32de8681fdb 100644
--- a/src/Dictionaries/DictionaryHelpers.h
+++ b/src/Dictionaries/DictionaryHelpers.h
@@ -600,6 +600,7 @@ void mergeBlockWithPipe(
     while (executor.pull(block))
     {
         convertToFullIfSparse(block);
+        block.checkNumberOfRows();
 
         Columns block_key_columns;
         block_key_columns.reserve(key_columns_size);