diff --git a/test/sum_avg_portable.cpp b/test/sum_avg_portable.cpp
index e31595e..fe73be8 100644
--- a/test/sum_avg_portable.cpp
+++ b/test/sum_avg_portable.cpp
@@ -25,7 +25,7 @@ void do_sum_avg(int values[], int n, int& sum, float& avg)
 }
 int main()
 {
-    boost::function4<void, int[], int, int&, float> sum_avg;
+    boost::function4<void, int[], int, int&, float&> sum_avg;
     sum_avg = &do_sum_avg;
 
     return 0;