diff --git a/include/boost/unordered/unordered_map.hpp b/include/boost/unordered/unordered_map.hpp
index d2793c56..b0658bad 100644
--- a/include/boost/unordered/unordered_map.hpp
+++ b/include/boost/unordered/unordered_map.hpp
@@ -105,8 +105,17 @@ namespace boost
         unordered_map(InputIterator f, InputIterator l,
                 size_type n,
                 const hasher &hf = hasher(),
-                const key_equal &eql = key_equal(),
-                const allocator_type &a = allocator_type())
+                const key_equal &eql = key_equal())
+            : base(f, l, n, hf, eql, allocator_type())
+        {
+        }
+
+        template <class InputIterator>
+        unordered_map(InputIterator f, InputIterator l,
+                size_type n,
+                const hasher &hf,
+                const key_equal &eql,
+                const allocator_type &a)
             : base(f, l, n, hf, eql, a)
         {
         }
@@ -560,8 +569,17 @@ namespace boost
         unordered_multimap(InputIterator f, InputIterator l,
                 size_type n,
                 const hasher &hf = hasher(),
-                const key_equal &eql = key_equal(),
-                const allocator_type &a = allocator_type())
+                const key_equal &eql = key_equal())
+          : base(f, l, n, hf, eql, allocator_type())
+        {
+        }
+
+        template <class InputIterator>
+        unordered_multimap(InputIterator f, InputIterator l,
+                size_type n,
+                const hasher &hf,
+                const key_equal &eql,
+                const allocator_type &a)
           : base(f, l, n, hf, eql, a)
         {
         }
diff --git a/include/boost/unordered/unordered_set.hpp b/include/boost/unordered/unordered_set.hpp
index 07ed746b..aecb54b4 100644
--- a/include/boost/unordered/unordered_set.hpp
+++ b/include/boost/unordered/unordered_set.hpp
@@ -103,8 +103,16 @@ namespace boost
         template <class InputIterator>
         unordered_set(InputIterator f, InputIterator l, size_type n,
                 const hasher &hf = hasher(),
-                const key_equal &eql = key_equal(),
-                const allocator_type &a = allocator_type())
+                const key_equal &eql = key_equal())
+            : base(f, l, n, hf, eql, allocator_type())
+        {
+        }
+        
+        template <class InputIterator>
+        unordered_set(InputIterator f, InputIterator l, size_type n,
+                const hasher &hf,
+                const key_equal &eql,
+                const allocator_type &a)
             : base(f, l, n, hf, eql, a)
         {
         }
@@ -530,8 +538,16 @@ namespace boost
         template <class InputIterator>
         unordered_multiset(InputIterator f, InputIterator l, size_type n,
                 const hasher &hf = hasher(),
-                const key_equal &eql = key_equal(),
-                const allocator_type &a = allocator_type())
+                const key_equal &eql = key_equal())
+          : base(f, l, n, hf, eql, allocator_type())
+        {
+        }
+
+        template <class InputIterator>
+        unordered_multiset(InputIterator f, InputIterator l, size_type n,
+                const hasher &hf,
+                const key_equal &eql,
+                const allocator_type &a)
           : base(f, l, n, hf, eql, a)
         {
         }