diff --git a/include/etl/deque.h b/include/etl/deque.h
index 0cdf4bfd..0511bb99 100644
--- a/include/etl/deque.h
+++ b/include/etl/deque.h
@@ -259,6 +259,7 @@ namespace etl
     struct iterator : public etl::iterator<ETL_OR_STD::random_access_iterator_tag, T>
     {
       friend class ideque;
+      friend struct const_iterator;
 
       //***************************************************
       iterator()
diff --git a/include/etl/forward_list.h b/include/etl/forward_list.h
index 5a551d77..968426a1 100644
--- a/include/etl/forward_list.h
+++ b/include/etl/forward_list.h
@@ -409,6 +409,7 @@ namespace etl
     public:
 
       friend class iforward_list;
+      friend class const_iterator;
 
       iterator()
         : p_node(nullptr)
diff --git a/include/etl/indirect_vector.h b/include/etl/indirect_vector.h
index 102583bf..6d62ff86 100644
--- a/include/etl/indirect_vector.h
+++ b/include/etl/indirect_vector.h
@@ -187,6 +187,7 @@ namespace etl
     public:
 
       friend class iindirect_vector;
+      friend class const_iterator;
 
       iterator()
       {
diff --git a/include/etl/intrusive_forward_list.h b/include/etl/intrusive_forward_list.h
index 33836cc4..9a70e4c8 100644
--- a/include/etl/intrusive_forward_list.h
+++ b/include/etl/intrusive_forward_list.h
@@ -333,6 +333,7 @@ namespace etl
     public:
 
       friend class intrusive_forward_list;
+      friend class const_iterator;
 
       iterator()
         : p_value(nullptr)
diff --git a/include/etl/intrusive_list.h b/include/etl/intrusive_list.h
index f618ef9b..a2db6f06 100644
--- a/include/etl/intrusive_list.h
+++ b/include/etl/intrusive_list.h
@@ -388,6 +388,7 @@ namespace etl
     public:
 
       friend class intrusive_list;
+      friend class const_iterator;
 
       iterator()
         : p_value(nullptr)
diff --git a/include/etl/list.h b/include/etl/list.h
index 6225d011..0cb5f65e 100644
--- a/include/etl/list.h
+++ b/include/etl/list.h
@@ -489,6 +489,7 @@ namespace etl
     public:
 
       friend class ilist;
+      friend class const_iterator;
 
       iterator()
         : p_node(nullptr)
diff --git a/include/etl/map.h b/include/etl/map.h
index 26b434c1..2a6180ed 100755
--- a/include/etl/map.h
+++ b/include/etl/map.h
@@ -584,6 +584,7 @@ namespace etl
     public:
 
       friend class imap;
+      friend class const_iterator;
 
       iterator()
         : p_map(nullptr)
diff --git a/include/etl/multimap.h b/include/etl/multimap.h
index 91586ea1..fc571e0a 100644
--- a/include/etl/multimap.h
+++ b/include/etl/multimap.h
@@ -742,6 +742,7 @@ namespace etl
     public:
 
       friend class imultimap;
+      friend class const_iterator;
 
       iterator()
         : p_multimap(nullptr)
diff --git a/include/etl/multiset.h b/include/etl/multiset.h
index ae4eb7fc..86b3cd9d 100644
--- a/include/etl/multiset.h
+++ b/include/etl/multiset.h
@@ -724,6 +724,7 @@ namespace etl
     public:
 
       friend class imultiset;
+      friend class const_iterator;
 
       iterator()
         : p_multiset(nullptr)
diff --git a/include/etl/reference_flat_map.h b/include/etl/reference_flat_map.h
index c5ac11c8..28445617 100644
--- a/include/etl/reference_flat_map.h
+++ b/include/etl/reference_flat_map.h
@@ -131,6 +131,7 @@ namespace etl
     public:
 
       friend class ireference_flat_map;
+      friend class const_iterator;
 
       iterator()
       {
diff --git a/include/etl/reference_flat_multimap.h b/include/etl/reference_flat_multimap.h
index 8a170cfa..eedd7a9e 100644
--- a/include/etl/reference_flat_multimap.h
+++ b/include/etl/reference_flat_multimap.h
@@ -106,6 +106,7 @@ namespace etl
     public:
 
       friend class ireference_flat_multimap;
+      friend class const_iterator;
 
       iterator()
       {
diff --git a/include/etl/reference_flat_set.h b/include/etl/reference_flat_set.h
index 94003f97..298b4403 100644
--- a/include/etl/reference_flat_set.h
+++ b/include/etl/reference_flat_set.h
@@ -125,6 +125,7 @@ namespace etl
     public:
 
       friend class ireference_flat_set;
+      friend class const_iterator;
 
       iterator()
       {
diff --git a/include/etl/set.h b/include/etl/set.h
index 31674b3d..bac167c2 100755
--- a/include/etl/set.h
+++ b/include/etl/set.h
@@ -561,6 +561,7 @@ namespace etl
     public:
 
       friend class iset;
+      friend class const_iterator;
 
       iterator()
         : p_set(nullptr)
diff --git a/include/etl/unordered_map.h b/include/etl/unordered_map.h
index c0a3bbf7..82c9052b 100644
--- a/include/etl/unordered_map.h
+++ b/include/etl/unordered_map.h
@@ -188,6 +188,7 @@ namespace etl
       typedef typename iunordered_map::size_type       size_type;
 
       friend class iunordered_map;
+      friend class const_iterator;
 
       //*********************************
       iterator()
diff --git a/include/etl/unordered_multimap.h b/include/etl/unordered_multimap.h
index 2e622058..df0841e1 100644
--- a/include/etl/unordered_multimap.h
+++ b/include/etl/unordered_multimap.h
@@ -187,6 +187,7 @@ namespace etl
       typedef typename iunordered_multimap::size_type       size_type;
 
       friend class iunordered_multimap;
+      friend class const_iterator;
 
       //*********************************
       iterator()
diff --git a/include/etl/unordered_multiset.h b/include/etl/unordered_multiset.h
index b8793407..56746d69 100644
--- a/include/etl/unordered_multiset.h
+++ b/include/etl/unordered_multiset.h
@@ -183,6 +183,7 @@ namespace etl
       typedef typename iunordered_multiset::size_type       size_type;
 
       friend class iunordered_multiset;
+      friend class const_iterator;
 
       //*********************************
       iterator()
diff --git a/include/etl/unordered_set.h b/include/etl/unordered_set.h
index 9fbc3586..df6b9753 100644
--- a/include/etl/unordered_set.h
+++ b/include/etl/unordered_set.h
@@ -184,6 +184,7 @@ namespace etl
       typedef typename iunordered_set::size_type       size_type;
 
       friend class iunordered_set;
+      friend class const_iterator;
 
       //*********************************
       iterator()