diff --git a/vcg/math/random_generator.h b/vcg/math/random_generator.h
index 2c2c800e..620f61e6 100644
--- a/vcg/math/random_generator.h
+++ b/vcg/math/random_generator.h
@@ -30,6 +30,8 @@
 
 #ifndef __VCG_RandomGenerator
 #define __VCG_RandomGenerator
+
+#include <functional>
 namespace vcg {
   namespace math {