diff --git a/dynamic_bitset.html b/dynamic_bitset.html
index 108527a..6cb66f8 100644
--- a/dynamic_bitset.html
+++ b/dynamic_bitset.html
@@ -198,7 +198,7 @@ public:
     dynamic_bitset <a href="#op-sl">operator&lt;&lt;</a>(size_type n) const;
     dynamic_bitset <a href="#op-sr">operator&gt;&gt;</a>(size_type n) const;
 
-    dynamic_bitset&amp; <a href="#set3">set</a>(size_type n, size_type len, bool val = true);
+    dynamic_bitset&amp; <a href="#set3">set</a>(size_type n, size_type len, bool val);
     dynamic_bitset&amp; <a href="#set2">set</a>(size_type n, bool val = true);
     dynamic_bitset&amp; <a href="#set1">set</a>();
     dynamic_bitset&amp; <a href="#reset3">reset</a>(size_type n, size_type len);
@@ -1069,7 +1069,7 @@ dynamic_bitset&amp; <a id="reset1">reset</a>()
 <hr />
 <pre>
 dynamic_bitset&amp; <a id=
-"set3">set</a>(size_type n, size_type len, bool val = true);
+"set3">set</a>(size_type n, size_type len, bool val);
 </pre>
 
 <b>Precondition:</b> <tt>n + len &lt; this-&gt;size()</tt>.<br />
diff --git a/include/boost/dynamic_bitset/dynamic_bitset.hpp b/include/boost/dynamic_bitset/dynamic_bitset.hpp
index 941332b..a128a69 100644
--- a/include/boost/dynamic_bitset/dynamic_bitset.hpp
+++ b/include/boost/dynamic_bitset/dynamic_bitset.hpp
@@ -281,7 +281,7 @@ public:
     dynamic_bitset operator>>(size_type n) const;
 
     // basic bit operations
-    dynamic_bitset& set(size_type n, size_type len, bool val = true);
+    dynamic_bitset& set(size_type n, size_type len, bool val /* = true */); // default would make it ambiguous
     dynamic_bitset& set(size_type n, bool val = true);
     dynamic_bitset& set();
     dynamic_bitset& reset(size_type n, size_type len);
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 53d1461..25cf932 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -15,6 +15,7 @@ test-suite dynamic_bitset :
     [ run dyn_bitset_unit_tests3.cpp : : : <library>/boost/system//boost_system ]
     [ run dyn_bitset_unit_tests4.cpp : : : <library>/boost/filesystem//boost_filesystem
                                            <library>/boost/system//boost_system ]
+    [ run test_ambiguous_set.cpp ]
     [ run test_lowest_bit.cpp ]
     ;
 
diff --git a/test/test_ambiguous_set.cpp b/test/test_ambiguous_set.cpp
new file mode 100644
index 0000000..ccc6508
--- /dev/null
+++ b/test/test_ambiguous_set.cpp
@@ -0,0 +1,30 @@
+//
+// Copyright (C) 2018 James E. King III
+// 
+// Permission to copy, use, modify, sell and distribute this software
+// is granted provided this copyright notice appears in all copies.
+// This software is provided "as is" without express or implied
+// warranty, and with no claim as to its suitability for any purpose.
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <boost/dynamic_bitset.hpp>
+#include <boost/detail/lightweight_test.hpp>
+
+int main(int, char*[])
+{
+    boost::dynamic_bitset<> x(5); // all 0's by default
+    x.set(1, 2);
+    x.set(3, 1, true);
+    x.set(2, 1, false);
+    BOOST_TEST(!x.test(0));
+    BOOST_TEST( x.test(1));
+    BOOST_TEST(!x.test(2));
+    BOOST_TEST( x.test(3));
+    BOOST_TEST(!x.test(4));
+
+    return boost::report_errors();
+}