diff --git a/src/bilangwriter.cc b/src/bilangwriter.cc
index 6555ee3..a6f1936 100644
--- a/src/bilangwriter.cc
+++ b/src/bilangwriter.cc
@@ -102,7 +102,7 @@ namespace warc2text{
         }
 
         for (size_t i = 0; i < lines.size(); ++i) {
-            result += lines[i] + "\t" + std::to_string(i) + ":" + std::to_string(lines.size()) + "\n";
+            result += lines[i] + "\t" + std::to_string(i + 1) + ":" + std::to_string(lines.size()) + "\n";
         }
 
         return result;