diff -Naur FORTE-0.3.5.orig/src/core/datatypes/forte_lreal.cpp FORTE-0.3.5/src/core/datatypes/forte_lreal.cpp
--- FORTE-0.3.5.orig/src/core/datatypes/forte_lreal.cpp	2008-12-11 16:05:26.000000000 +0000
+++ FORTE-0.3.5/src/core/datatypes/forte_lreal.cpp	2009-02-16 11:01:44.000000000 +0000
@@ -8,6 +8,7 @@
  * Contributors:
  *     <date>: <author>, <author email> - changes
  *******************************************************************************/
+#include <stdlib.h>
 #include <math.h>
 #include "forte_lreal.h"
 
diff -Naur FORTE-0.3.5.orig/src/core/datatypes/forte_real.cpp FORTE-0.3.5/src/core/datatypes/forte_real.cpp
--- FORTE-0.3.5.orig/src/core/datatypes/forte_real.cpp	2008-12-11 16:05:40.000000000 +0000
+++ FORTE-0.3.5/src/core/datatypes/forte_real.cpp	2009-02-16 11:12:16.000000000 +0000
@@ -8,6 +8,7 @@
  * Contributors:
  *     <date>: <author>, <author email> - changes
  *******************************************************************************/
+#include <stdlib.h>
 #include <math.h>
 #include "forte_real.h"