diff --git a/CaloDigi/Realistic/src/RealisticCaloDigi.cc b/CaloDigi/Realistic/src/RealisticCaloDigi.cc
index 6f37fce5..5fb60c93 100644
--- a/CaloDigi/Realistic/src/RealisticCaloDigi.cc
+++ b/CaloDigi/Realistic/src/RealisticCaloDigi.cc
@@ -12,6 +12,7 @@
 #include <UTIL/CellIDDecoder.h>
 #include <marlin/ProcessorEventSeeder.h>
 
+#include <algorithm>
 #include <iostream>
 #include <string>
 #include <assert.h>