diff --git a/src/sequencing-manager.cpp b/src/sequencing-manager.cpp
index 01a22fa..b988d9c 100644
--- a/src/sequencing-manager.cpp
+++ b/src/sequencing-manager.cpp
@@ -55,7 +55,7 @@
 }
 
 void
-SequencingManager::writeSeqNoToFile()
+SequencingManager::writeSeqNoToFile() const
 {
   std::ofstream outputFile(m_seqFileNameWithPath.c_str(), ios::binary);
   outputFile << m_combinedSeqNo;