diff --git a/CMakeLists.txt b/CMakeLists.txt
index 30adff52..bbc1797b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -860,7 +860,6 @@ SET (hs_compile_SRCS
     src/nfagraph/ng_stop.h
     src/nfagraph/ng_uncalc_components.cpp
     src/nfagraph/ng_uncalc_components.h
-    src/nfagraph/ng_undirected.h
     src/nfagraph/ng_utf8.cpp
     src/nfagraph/ng_utf8.h
     src/nfagraph/ng_util.cpp
diff --git a/src/nfagraph/ng_repeat.cpp b/src/nfagraph/ng_repeat.cpp
index 048ee43f..1f63ad3c 100644
--- a/src/nfagraph/ng_repeat.cpp
+++ b/src/nfagraph/ng_repeat.cpp
@@ -38,7 +38,6 @@
 #include "ng_prune.h"
 #include "ng_reports.h"
 #include "ng_som_util.h"
-#include "ng_undirected.h"
 #include "ng_util.h"
 #include "nfa/accel.h"
 #include "nfa/limex_limits.h"
diff --git a/src/nfagraph/ng_undirected.h b/src/nfagraph/ng_undirected.h
deleted file mode 100644
index 036adcbf..00000000
--- a/src/nfagraph/ng_undirected.h
+++ /dev/null
@@ -1,136 +0,0 @@
-/*
- * Copyright (c) 2015-2017, Intel Corporation
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- *  * Redistributions of source code must retain the above copyright notice,
- *    this list of conditions and the following disclaimer.
- *  * Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *  * Neither the name of Intel Corporation nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- */
-
-/** \file
- * \brief Create an undirected graph from an NFAGraph.
- */
-
-#ifndef NG_UNDIRECTED_H
-#define NG_UNDIRECTED_H
-
-#include "ng_holder.h"
-#include "ng_util.h"
-#include "ue2common.h"
-#include "util/graph_range.h"
-#include "util/unordered.h"
-
-#include <vector>
-
-#include <boost/graph/adjacency_list.hpp>
-
-namespace ue2 {
-
-/**
- * \brief BGL graph type for the undirected NFA graph.
- *
- * Note that we use a set for the out-edge lists: this avoids the construction
- * of parallel edges. The only vertex property constructed is \a
- * vertex_index_t.
- */
-using NFAUndirectedGraph = boost::adjacency_list<
-    boost::listS,                                    // out edges
-    boost::listS,                                    // vertices
-    boost::undirectedS,                              // graph is undirected
-    boost::property<boost::vertex_index_t, size_t>>; // vertex properties
-
-using NFAUndirectedVertex = NFAUndirectedGraph::vertex_descriptor;
-
-/**
- * Make a copy of an NFAGraph with undirected edges, optionally without start
- * vertices. Mappings from the original graph to the new one are provided.
- *
- * Note that new vertex indices are assigned contiguously in \a vertices(g)
- * order.
- */
-template <typename Graph>
-NFAUndirectedGraph createUnGraph(const Graph &g,
-           bool excludeStarts,
-           bool excludeAccepts,
-           std::unordered_map<typename Graph::vertex_descriptor,
-                              NFAUndirectedVertex> &old2new) {
-    NFAUndirectedGraph ug;
-    size_t idx = 0;
-
-    assert(old2new.empty());
-    old2new.reserve(num_vertices(g));
-
-    for (auto v : ue2::vertices_range(g)) {
-        // skip all accept nodes
-        if (excludeAccepts && is_any_accept(v, g)) {
-            continue;
-        }
-
-        // skip starts if required
-        if (excludeStarts && is_any_start(v, g)) {
-            continue;
-        }
-
-        auto nuv = boost::add_vertex(ug);
-        old2new.emplace(v, nuv);
-        boost::put(boost::vertex_index, ug, nuv, idx++);
-    }
-
-    // Track seen edges so that we don't insert parallel edges.
-    using Vertex = typename Graph::vertex_descriptor;
-    ue2_unordered_set<std::pair<Vertex, Vertex>> seen;
-    seen.reserve(num_edges(g));
-    auto make_ordered_edge = [](Vertex a, Vertex b) {
-        return std::make_pair(std::min(a, b), std::max(a, b));
-    };
-
-    for (const auto &e : ue2::edges_range(g)) {
-        auto u = source(e, g);
-        auto v = target(e, g);
-
-        if ((excludeAccepts && is_any_accept(u, g))
-            || (excludeStarts && is_any_start(u, g))) {
-            continue;
-        }
-
-        if ((excludeAccepts && is_any_accept(v, g))
-            || (excludeStarts && is_any_start(v, g))) {
-            continue;
-        }
-
-        if (!seen.emplace(make_ordered_edge(u, v)).second) {
-            continue; // skip parallel edge.
-        }
-
-        NFAUndirectedVertex new_u = old2new.at(u);
-        NFAUndirectedVertex new_v = old2new.at(v);
-
-        boost::add_edge(new_u, new_v, ug);
-    }
-
-    assert(!has_parallel_edge(ug));
-    return ug;
-}
-
-} // namespace ue2
-
-#endif /* NG_UNDIRECTED_H */