diff --git a/cpp/include/IceUtil/Timer.h b/cpp/include/IceUtil/Timer.h
index 177a7f8..19b8c09 100644
--- a/cpp/include/IceUtil/Timer.h
+++ b/cpp/include/IceUtil/Timer.h
@@ -12,6 +12,7 @@
 
 #include <set>
 #include <map>
+#include <functional>
 
 namespace IceUtil
 {