diff --git a/nonlin.cpp b/nonlin.cpp
index 82cbd83a5bcbd741672773761b61224d04bbe7b2..e3bd9d80977c658e33ecde51797794b43bb2189d 100644
--- a/nonlin.cpp
+++ b/nonlin.cpp
@@ -10,6 +10,7 @@
 #include "newmatio.h"
 #include "bfmatrix.h"
 #include "nonlin.h"
+#include "utils/fsl_isfinite.h"
 
 using namespace std;
 using namespace NEWMAT;