diff --git a/src/Functions/PositionImpl.h b/src/Functions/PositionImpl.h
index 9bebff0e130..a8b95f6f546 100644
--- a/src/Functions/PositionImpl.h
+++ b/src/Functions/PositionImpl.h
@@ -370,10 +370,14 @@ struct PositionImpl
         {
             size_t needle_size = needle_offsets[i] - prev_needle_offset - 1;
             size_t haystack_size = haystack_offsets[i] - prev_haystack_offset - 1;
+            
+            size_t haystack_chars_size = Impl::countChars(
+                reinterpret_cast<const char *>(&haystack_data[prev_haystack_offset]),
+                reinterpret_cast<const char *>(&haystack_data[haystack_offsets[i] - 1]));
 
             auto start = start_pos != nullptr ? std::max(start_pos->getUInt(i), UInt64(1)) : UInt64(1);
 
-            if (start > haystack_size + 1)
+            if (start > haystack_chars_size + 1)
             {
                 res[i] = 0;
             }
@@ -429,13 +433,15 @@ struct PositionImpl
         /// NOTE You could use haystack indexing. But this is a rare case.
         ColumnString::Offset prev_needle_offset = 0;
 
+        size_t haystack_size = Impl::countChars(haystack.data(), haystack.data() + haystack.size());
+
         for (size_t i = 0; i < input_rows_count; ++i)
         {
             size_t needle_size = needle_offsets[i] - prev_needle_offset - 1;
 
             auto start = start_pos != nullptr ? std::max(start_pos->getUInt(i), UInt64(1)) : UInt64(1);
 
-            if (start > haystack.size() + 1)
+            if (start > haystack_size + 1)
             {
                 res[i] = 0;
             }