diff --git a/src/Datafile.cpp b/src/Datafile.cpp
index bf133fee..1180993b 100644
--- a/src/Datafile.cpp
+++ b/src/Datafile.cpp
@@ -81,12 +81,14 @@ void Datafile::addExclusion (const std::string& exclusion)
 ////////////////////////////////////////////////////////////////////////////////
 void Datafile::addInterval (const Interval& interval)
 {
+  _lines_added.push_back (interval.serialize ());
   _dirty = true;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 void Datafile::modifyInterval (const Interval& interval)
 {
+  _lines_modified.push_back (interval.serialize ());
   _dirty = true;
 }
 
diff --git a/src/Datafile.h b/src/Datafile.h
index 38639bf3..0f5f1526 100644
--- a/src/Datafile.h
+++ b/src/Datafile.h
@@ -55,6 +55,10 @@ private:
 
 private:
   File                      _file           {};
+  std::vector <std::string> _lines          {};
+  std::vector <std::string> _lines_added    {};
+  std::vector <std::string> _lines_modified {};
+  bool                      _lines_loaded   {false};
   bool                      _dirty          {false};
   Datetime                  _day1           {0};
   Datetime                  _dayN           {0};