diff --git a/lib/parallelIO/GridNerscIO.h b/lib/parallelIO/GridNerscIO.h
index 5d1e2e41..4dfa7979 100644
--- a/lib/parallelIO/GridNerscIO.h
+++ b/lib/parallelIO/GridNerscIO.h
@@ -5,6 +5,7 @@
 #include <iostream>
 #include <iomanip>
 #include <fstream>
+#include <map>
 
 #ifdef HAVE_ENDIAN_H
 #include <endian.h>