diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8329c0ba..85d97b9b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -991,6 +991,7 @@ SET (hs_SRCS
     src/util/fatbit_build.h
     src/util/graph.h
     src/util/hash.h
+    src/util/hash_dynamic_bitset.h
     src/util/math.h
     src/util/multibit_build.cpp
     src/util/multibit_build.h
diff --git a/src/nfagraph/ng_mcclellan.cpp b/src/nfagraph/ng_mcclellan.cpp
index 375086a4..e061084e 100644
--- a/src/nfagraph/ng_mcclellan.cpp
+++ b/src/nfagraph/ng_mcclellan.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2016, Intel Corporation
+ * 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:
@@ -42,6 +42,8 @@
 #include "util/bitfield.h"
 #include "util/determinise.h"
 #include "util/graph_range.h"
+#include "util/hash.h"
+#include "util/hash_dynamic_bitset.h"
 #include "util/make_unique.h"
 #include "util/report_manager.h"
 #include "util/ue2_containers.h"
@@ -467,7 +469,7 @@ public:
 
 struct Big_Traits {
     using StateSet = dynamic_bitset<>;
-    using StateMap = map<StateSet, dstate_id_t>;
+    using StateMap = unordered_map<StateSet, dstate_id_t, hash_dynamic_bitset>;
 
     static StateSet init_states(u32 num) {
         return StateSet(num);
diff --git a/src/util/hash_dynamic_bitset.h b/src/util/hash_dynamic_bitset.h
new file mode 100644
index 00000000..315aed34
--- /dev/null
+++ b/src/util/hash_dynamic_bitset.h
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 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 Hashing utility functions.
+ */
+
+#ifndef UTIL_HASH_DYNAMIC_BITSET_H
+#define UTIL_HASH_DYNAMIC_BITSET_H
+
+#include <boost/dynamic_bitset.hpp>
+#include <boost/functional/hash/hash.hpp>
+
+#include <iterator>
+
+namespace ue2 {
+
+/**
+ * \brief An output iterator which calculates the combined hash of all elements
+ * written to it.
+ *
+ * The location to output the hash is provided to the constructor and should
+ * already be zero initialised.
+ */
+struct hash_output_it {
+    using value_type = void;
+    using difference_type = ptrdiff_t;
+    using pointer = void *;
+    using reference = void;
+    using iterator_category = std::output_iterator_tag;
+
+    hash_output_it(size_t *hash_out = nullptr) : out(hash_out) {}
+    hash_output_it &operator++() {
+        return *this;
+    }
+    hash_output_it &operator++(int) {
+        return *this;
+    }
+
+    struct deref_proxy {
+        deref_proxy(size_t *hash_out) : out(hash_out) {}
+
+        template<typename T>
+        void operator=(const T &val) const {
+            boost::hash_combine(*out, val);
+        }
+
+    private:
+        size_t *out; /* output location of the owning iterator */
+    };
+
+    deref_proxy operator*() { return {out}; }
+
+private:
+    size_t *out; /* location to output the hashes to */
+};
+
+/* Function object for hashing a dynamic bitset */
+struct hash_dynamic_bitset {
+    size_t operator()(const boost::dynamic_bitset<> &bs) const {
+        size_t rv = 0;
+        to_block_range(bs, hash_output_it(&rv));
+        return rv;
+    }
+};
+
+} // namespace ue2
+
+#endif