diff --git a/arbor/util/piecewise.hpp b/arbor/util/piecewise.hpp
index ff83d6ea01..f047b2bbdd 100644
--- a/arbor/util/piecewise.hpp
+++ b/arbor/util/piecewise.hpp
@@ -103,7 +103,6 @@
 
 #include "util/iterutil.hpp"
 #include "util/transform.hpp"
-#include "util/meta.hpp"
 #include "util/partition.hpp"
 
 namespace arb {
@@ -160,8 +159,8 @@ struct pw_element_proxy {
         extent(pw.extent(i)), value(pw.value(i)) {}
 
     operator pw_element<X>() const { return pw_element<X>{extent, value}; }
-    operator X() const { return value; }
-    pw_element_proxy& operator=(X x) {value = std::move(x); return *this; };
+    operator X&() const { return value; }
+    pw_element_proxy& operator=(X x) { value = std::move(x); return *this; };
 
     double lower_bound() const { return extent.first; }
     double upper_bound() const { return extent.second; }
@@ -170,6 +169,21 @@ struct pw_element_proxy {
     X& value;
 };
 
+template <typename X>
+struct pw_element_proxy<const X> {
+    pw_element_proxy(const pw_elements<X>& pw, pw_size_type i):
+        extent(pw.extent(i)), value(pw.value(i)) {}
+
+    operator pw_element<X>() const { return pw_element<X>{extent, value}; }
+    operator const X&() const { return value; }
+
+    double lower_bound() const { return extent.first; }
+    double upper_bound() const { return extent.second; }
+
+    const std::pair<double, double> extent;
+    const X& value;
+};
+
 // Compute indices into vertex set corresponding to elements that cover a point x:
 
 namespace {
@@ -239,12 +253,12 @@ struct pw_elements {
         const_iterator(): pw_(nullptr) {}
 
         using value_type = pw_element<X>;
-        using pointer = const pointer_proxy<pw_element<X>>;
-        using reference = pw_element<X>;
+        using pointer = const pointer_proxy<pw_element_proxy<const X>>;
+        using reference = pw_element_proxy<const X>;
 
-        reference operator[](difference_type j) const { return (*pw_)[j+*c_]; }
-        reference operator*() const { return (*pw_)[*c_]; }
-        pointer operator->() const { return pointer{(*pw_)[*c_]}; }
+        reference operator[](difference_type j) const { return {*pw_, j + *c_}; }
+        reference operator*() const { return {*pw_, *c_}; }
+        pointer operator->() const { return pointer{reference{*pw_, *c_}}; }
 
         // (required for iterator_adaptor)
         counter<pw_size_type>& inner() { return c_; }
diff --git a/arbor/util/pw_over_cable.hpp b/arbor/util/pw_over_cable.hpp
index ee699a9fcb..73ce40e0a9 100644
--- a/arbor/util/pw_over_cable.hpp
+++ b/arbor/util/pw_over_cable.hpp
@@ -16,7 +16,10 @@ struct get_value {
 // Convert mcable_map values to a piecewise function over an mcable.
 // The projection gives the map from the values in the mcable_map to the values in the piecewise function.
 template <typename T, typename U, typename Proj = impl::get_value>
-util::pw_elements<U> pw_over_cable(const mcable_map<T>& mm, mcable cable, U dflt_value, Proj projection = Proj{}) {
+util::pw_elements<U> pw_over_cable(const mcable_map<T>& mm,
+                                   mcable cable,
+                                   U dflt_value,
+                                   Proj projection = Proj{}) {
     using value_type = typename mcable_map<T>::value_type;
     msize_t bid = cable.branch;
 
@@ -26,8 +29,11 @@ util::pw_elements<U> pw_over_cable(const mcable_map<T>& mm, mcable cable, U dflt
         as_branch(msize_t x): value(x) {}
     };
 
-    auto map_on_branch = util::make_range(
-        std::equal_range(mm.begin(), mm.end(), bid, [](as_branch a, as_branch b) { return a.value<b.value; }));
+    auto map_on_branch = util::make_range(std::equal_range(mm.begin(), mm.end(),
+                                                           bid,
+                                                           [](as_branch a, as_branch b) {
+                                                               return a.value < b.value;
+                                                           }));
 
     if (map_on_branch.empty()) {
         return util::pw_elements<U>({cable.prox_pos, cable.dist_pos}, {dflt_value});