diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 11bc183cc..a8ebc8662 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -202,69 +202,6 @@ public:
     ~CoroutineContext() {};
 };
 
-std::unique_ptr<FinishSink> sourceToSink(std::function<void(Source &)> fun)
-{
-    struct SourceToSink : FinishSink
-    {
-        typedef boost::coroutines2::coroutine<bool> coro_t;
-
-        std::function<void(Source &)> fun;
-        std::optional<coro_t::push_type> coro;
-
-        SourceToSink(std::function<void(Source &)> fun) : fun(fun)
-        {
-        }
-
-        std::string_view cur;
-
-        void operator () (std::string_view in) override
-        {
-            if (in.empty()) return;
-            cur = in;
-
-            if (!coro) {
-                CoroutineContext ctx;
-                coro = coro_t::push_type(VirtualStackAllocator{}, [&](coro_t::pull_type & yield) {
-                    LambdaSource source([&](char *out, size_t out_len) {
-                        if (cur.empty()) {
-                            yield();
-                            if (yield.get()) {
-                                throw EndOfFile("coroutine exhausted");
-                            }
-                        }
-
-                        size_t n = std::min(cur.size(), out_len);
-                        memcpy(out, cur.data(), n);
-                        cur.remove_prefix(n);
-                        return n;
-                    });
-                    fun(source);
-                });
-            }
-
-            if (!*coro) { abort(); }
-
-            if (!cur.empty()) {
-                CoroutineContext ctx;
-                (*coro)(false);
-            }
-        }
-
-        void finish() override
-        {
-            if (!coro) return;
-            if (!*coro) abort();
-            {
-                CoroutineContext ctx;
-                (*coro)(true);
-            }
-            if (*coro) abort();
-        }
-    };
-
-    return std::make_unique<SourceToSink>(fun);
-}
-
 
 std::unique_ptr<Source> sinkToSource(std::function<void(Sink &)> fun)
 {
diff --git a/src/libutil/serialise.hh b/src/libutil/serialise.hh
index 2a2568224..b9e16f6bd 100644
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -359,8 +359,6 @@ private:
     Bytes buf{};
 };
 
-std::unique_ptr<FinishSink> sourceToSink(std::function<void(Source &)> fun);
-
 /**
  * Convert a function that feeds data into a Sink into a Source. The
  * Source executes the function as a coroutine.