diff --git a/atrip.org b/atrip.org
index e5529fd..9ddedbd 100644
--- a/atrip.org
+++ b/atrip.org
@@ -1142,6 +1142,7 @@ namespace atrip {
 
 #include <vector>
 #include <array>
+#include <numeric>
 
 #include <atrip/Utils.hpp>
 #include <atrip/Debug.hpp>
@@ -1190,7 +1191,8 @@ namespace atrip {
             ==
             ( std::accumulate(n_tuples_per_rank.begin(),
                               n_tuples_per_rank.end(),
-                              0UL)
+                              0UL,
+                              std::plus<size_t>())
             + nExtraInvalid
             ));
   #endif
diff --git a/include/atrip/Tuples.hpp b/include/atrip/Tuples.hpp
index 83f6237..090eb9b 100644
--- a/include/atrip/Tuples.hpp
+++ b/include/atrip/Tuples.hpp
@@ -3,6 +3,7 @@
 
 #include <vector>
 #include <array>
+#include <numeric>
 
 #include <atrip/Utils.hpp>
 #include <atrip/Debug.hpp>
@@ -51,7 +52,8 @@ namespace atrip {
             ==
             ( std::accumulate(n_tuples_per_rank.begin(),
                               n_tuples_per_rank.end(),
-                              0UL)
+                              0UL,
+                              std::plus<size_t>())
             + nExtraInvalid
             ));
   #endif