diff --git a/vector.cpp b/vector.cpp
index 1dea169f..64afc489 100644
--- a/vector.cpp
+++ b/vector.cpp
@@ -101,10 +101,10 @@ util::vector<S,T>::normalised (void) const {
 //-----------------------------------------------------------------------------
 template <typename T>
 util::vector<2,T>
-util::polar_to_cartesian (const util::vector<2,T> &v) {
+util::polar_to_cartesian (util::vector<2,T> v) {
     return util::vector<2,T> {
-        v.r * std::cos (v.t),
-        v.r * std::sin (v.t)
+        v[0] * std::cos (v[1]),
+        v[0] * std::sin (v[1])
     };
 }
 
@@ -232,8 +232,11 @@ INSTANTIATE(int64_t)
 INSTANTIATE(float)
 INSTANTIATE(double)
 
+
 //-----------------------------------------------------------------------------
 namespace util {
+    template vector<2,float> polar_to_cartesian (util::vector<2,float>);
+
     template <> vector<1,float> random (void) { util::vector<1,float> out; randomise (out.data); return out; }
     template <> vector<2,float> random (void) { util::vector<2,float> out; randomise (out.data); return out; }
     template <> vector<3,float> random (void) { util::vector<3,float> out; randomise (out.data); return out; }
diff --git a/vector.hpp b/vector.hpp
index 8379e925..ce36af7b 100644
--- a/vector.hpp
+++ b/vector.hpp
@@ -56,7 +56,7 @@ namespace util {
     };
 
     // free vector operators
-    template <typename T> vector<2,T> polar_to_cartesian (const vector<2,T>&);
+    template <typename T> vector<2,T> polar_to_cartesian (vector<2,T>);
 
     template <typename T> vector<3,T> cross (const vector<3,T>&, const vector<3,T>&);
     template <typename T> vector<3,T> spherical_to_cartesian (const vector<3,T>&);