diff --git a/hanabi_learning_environment/hanabi_lib/canonical_encoders.cc b/hanabi_learning_environment/hanabi_lib/canonical_encoders.cc
index b7704399..b80b36a2 100644
--- a/hanabi_learning_environment/hanabi_lib/canonical_encoders.cc
+++ b/hanabi_learning_environment/hanabi_lib/canonical_encoders.cc
@@ -16,6 +16,7 @@
 #include <cassert>
 #include <cstdlib>
 #include <iostream>
+#include <numeric>
 #include <vector>
 
 #include "canonical_encoders.h"