diff --git a/include/mxx/reduction.hpp b/include/mxx/reduction.hpp
index 7fb7bb5..a84b995 100644
--- a/include/mxx/reduction.hpp
+++ b/include/mxx/reduction.hpp
@@ -731,7 +731,7 @@ inline std::vector<T> local_scan(const std::vector<T>& in) {
 // global scans
 
 template <typename InIterator, typename OutIterator, typename Func>
-void global_scan(InIterator begin, InIterator end, OutIterator out, Func func, const mxx::comm& comm = mxx::comm(), const bool commutative = true) {
+void global_scan(InIterator begin, InIterator end, OutIterator out, Func func, const bool commutative, const mxx::comm& comm = mxx::comm()) {
     OutIterator o = out;
     size_t n = std::distance(begin, end);
     // create subcommunicator for those processes which contain elements
@@ -753,10 +753,15 @@ void global_scan(InIterator begin, InIterator end, OutIterator out, Func func, c
     }
 }
 
+template <typename InIterator, typename OutIterator, typename Func>
+void global_scan(InIterator begin, InIterator end, OutIterator out, Func func, const mxx::comm& comm = mxx::comm()) {
+    global_scan(begin, end, out, func, true, comm);
+}
+
 
 // inplace!
 template <typename Iterator, typename Func>
-inline void global_scan_inplace(Iterator begin, Iterator end, Func func, const mxx::comm& comm = mxx::comm(), const bool commutative = true) {
+inline void global_scan_inplace(Iterator begin, Iterator end, Func func, const bool commutative, const mxx::comm& comm = mxx::comm()) {
     Iterator o = begin;
     size_t n = std::distance(begin, end);
     mxx::comm nonzero_comm = comm.split(n > 0);
@@ -776,38 +781,55 @@ inline void global_scan_inplace(Iterator begin, Iterator end, Func func, const m
     }
 }
 
+template <typename Iterator, typename Func>
+inline void global_scan_inplace(Iterator begin, Iterator end, Func func, const mxx::comm& comm = mxx::comm()) {
+    global_scan_inplace(begin, end, func, true, comm);
+}
+
 template <typename InIterator, typename OutIterator>
 inline void global_scan(InIterator begin, InIterator end, OutIterator out, const mxx::comm& comm = mxx::comm()) {
-    return global_scan(begin, end, out, std::plus<typename std::iterator_traits<OutIterator>::value_type>(), comm);
+    return global_scan(begin, end, out, std::plus<typename std::iterator_traits<OutIterator>::value_type>(), true, comm);
 }
 
 template <typename Iterator>
 inline void global_scan_inplace(Iterator begin, Iterator end, const mxx::comm& comm = mxx::comm()) {
-    return global_scan_inplace(begin, end, std::plus<typename std::iterator_traits<Iterator>::value_type>(), comm);
+    return global_scan_inplace(begin, end, std::plus<typename std::iterator_traits<Iterator>::value_type>(), true, comm);
 }
 
 // std::vector overloads
 template <typename T, typename Func>
-inline void global_scan_inplace(std::vector<T>& in, Func func, const mxx::comm& comm = mxx::comm(), const bool commutative = true) {
-    global_scan_inplace(in.begin(), in.end(), func, comm, commutative);
+inline void global_scan_inplace(std::vector<T>& in, Func func, const bool commutative, const mxx::comm& comm = mxx::comm()) {
+    global_scan_inplace(in.begin(), in.end(), func, commutative, comm);
+}
+
+template <typename T, typename Func>
+inline void global_scan_inplace(std::vector<T>& in, Func func, const mxx::comm& comm = mxx::comm()) {
+    global_scan_inplace(in.begin(), in.end(), func, true, comm);
 }
 
 template <typename T>
 inline void global_scan_inplace(std::vector<T>& in, const mxx::comm& comm = mxx::comm()) {
-    global_scan_inplace(in.begin(), in.end(), std::plus<T>(), comm);
+    global_scan_inplace(in.begin(), in.end(), std::plus<T>(), true, comm);
+}
+
+template <typename T, typename Func>
+inline std::vector<T> global_scan(const std::vector<T>& in, Func func, const bool commutative, const mxx::comm& comm = mxx::comm()) {
+    std::vector<T> result(in.size());
+    global_scan(in.begin(), in.end(), result.begin(), func, commutative, comm);
+    return result;
 }
 
 template <typename T, typename Func>
-inline std::vector<T> global_scan(const std::vector<T>& in, Func func, const mxx::comm& comm = mxx::comm(), const bool commutative = true) {
+inline std::vector<T> global_scan(const std::vector<T>& in, Func func, const mxx::comm& comm = mxx::comm()) {
     std::vector<T> result(in.size());
-    global_scan(in.begin(), in.end(), result.begin(), func, comm, commutative);
+    global_scan(in.begin(), in.end(), result.begin(), func, true, comm);
     return result;
 }
 
 template <typename T>
 inline std::vector<T> global_scan(const std::vector<T>& in, const mxx::comm& comm = mxx::comm()) {
     std::vector<T> result(in.size());
-    global_scan(in.begin(), in.end(), result.begin(), std::plus<T>(), comm);
+    global_scan(in.begin(), in.end(), result.begin(), std::plus<T>(), true, comm);
     return result;
 }