diff --git a/include/boost/function/function_base.hpp b/include/boost/function/function_base.hpp
index e8f318e..773cf5f 100644
--- a/include/boost/function/function_base.hpp
+++ b/include/boost/function/function_base.hpp
@@ -21,6 +21,7 @@
 #include <memory>
 #include <new>
 #include <boost/config.hpp>
+#include <boost/assert.hpp>
 #include <boost/type_traits/arithmetic_traits.hpp>
 #include <boost/type_traits/composite_traits.hpp>
 #include <boost/type_traits/is_stateless.hpp>
diff --git a/include/boost/function/function_template.hpp b/include/boost/function/function_template.hpp
index 3d4c72c..47f2fa2 100644
--- a/include/boost/function/function_template.hpp
+++ b/include/boost/function/function_template.hpp
@@ -296,7 +296,10 @@ namespace boost {
 #ifndef BOOST_FUNCTION_NO_ENABLE_IF
     BOOST_FUNCTION_FUNCTION(clear_type*) : function_base(), invoker(0) {}
 #else
-    BOOST_FUNCTION_FUNCTION(int) : function_base(), invoker(0) {}
+    BOOST_FUNCTION_FUNCTION(int zero) : function_base(), invoker(0)
+    {
+      BOOST_ASSERT(zero == 0);
+    }
 #endif
 
     BOOST_FUNCTION_FUNCTION(const BOOST_FUNCTION_FUNCTION& f) :
@@ -351,8 +354,9 @@ namespace boost {
       return *this;
     }
 #else
-    BOOST_FUNCTION_FUNCTION& operator=(int)
+    BOOST_FUNCTION_FUNCTION& operator=(int zero)
     {
+      BOOST_ASSERT(zero == 0);
       this->clear();
       return *this;
     }