diff --git a/include/boost/iostreams/detail/adapter/mode_adapter.hpp b/include/boost/iostreams/detail/adapter/mode_adapter.hpp
index 6486d52..f267bee 100755
--- a/include/boost/iostreams/detail/adapter/mode_adapter.hpp
+++ b/include/boost/iostreams/detail/adapter/mode_adapter.hpp
@@ -42,7 +42,7 @@ public:
           #endif
           localizable_tag
         { };
-    mode_adapter(const policy_type& t) : t_(t) { }
+    explicit mode_adapter(const policy_type& t) : t_(t) { }
 
         // Device member functions.
 
diff --git a/include/boost/iostreams/detail/adapter/output_iterator_adapter.hpp b/include/boost/iostreams/detail/adapter/output_iterator_adapter.hpp
index edc08a2..75127f4 100755
--- a/include/boost/iostreams/detail/adapter/output_iterator_adapter.hpp
+++ b/include/boost/iostreams/detail/adapter/output_iterator_adapter.hpp
@@ -25,7 +25,7 @@ public:
     BOOST_STATIC_ASSERT((is_convertible<Mode, output>::value));
     typedef Ch        char_type;
     typedef sink_tag  io_category;
-    output_iterator_adapter(OutIt out) : out_(out) { }
+    explicit output_iterator_adapter(OutIt out) : out_(out) { }
     void write(const char_type* s, std::streamsize n) 
     { std::copy(s, s + n, out_); }
 private:
diff --git a/include/boost/iostreams/detail/adapter/range_adapter.hpp b/include/boost/iostreams/detail/adapter/range_adapter.hpp
index cc7929a..23ed745 100755
--- a/include/boost/iostreams/detail/adapter/range_adapter.hpp
+++ b/include/boost/iostreams/detail/adapter/range_adapter.hpp
@@ -50,7 +50,7 @@ public:
             >::type                                  tag;
     typedef range_adapter_impl<tag>                  impl;
 
-    range_adapter(const Range& rng);
+    explicit range_adapter(const Range& rng);
     range_adapter(iterator first, iterator last);
     std::streamsize read(char_type* s, std::streamsize n);
     void write(const char_type* s, std::streamsize n);