diff --git a/eo/src/eoFunctor.h b/eo/src/eoFunctor.h
index 78202e84b..5ccf2e676 100644
--- a/eo/src/eoFunctor.h
+++ b/eo/src/eoFunctor.h
@@ -28,6 +28,7 @@
 #define _eoFunctor_h
 
 #include <functional>
+#include <string>
 
 /** @addtogroup Core
  * @{