diff --git a/eo/src/eoNDSorting.h b/eo/src/eoNDSorting.h
index c6dccbfb..a0f72656 100644
--- a/eo/src/eoNDSorting.h
+++ b/eo/src/eoNDSorting.h
@@ -27,6 +27,7 @@
 #ifndef eoNDSorting_h
 #define eoNDSorting_h
 
+#include <EO.h>
 #include <algorithm>
 #include <eoPop.h>
 #include <eoPerf2Worth.h>