Index: uspace/lib/cpp/include/impl/unordered_set.hpp
===================================================================
--- uspace/lib/cpp/include/impl/unordered_set.hpp	(revision 8830faae3dc30d687ce5dbe1a747c51eb961fe2a)
+++ uspace/lib/cpp/include/impl/unordered_set.hpp	(revision 2cb7f532a1e6ed120698f25f48b2049788008513)
@@ -450,6 +450,6 @@
 
             template<class K, class H, class P, class A>
-            friend bool operator==(unordered_set<K, H, P, A>&,
-                                   unordered_set<K, H, P, A>&);
+            friend bool operator==(const unordered_set<K, H, P, A>&,
+                                   const unordered_set<K, H, P, A>&);
     };
 
@@ -866,6 +866,6 @@
 
             template<class K, class H, class P, class A>
-            friend bool operator==(unordered_multiset<K, H, P, A>&,
-                                   unordered_multiset<K, H, P, A>&);
+            friend bool operator==(const unordered_multiset<K, H, P, A>&,
+                                   const unordered_multiset<K, H, P, A>&);
     };
 
@@ -887,6 +887,6 @@
 
     template<class Key, class Hash, class Pred, class Alloc>
-    bool operator==(unordered_set<Key, Hash, Pred, Alloc>& lhs,
-                    unordered_set<Key, Hash, Pred, Alloc>& rhs)
+    bool operator==(const unordered_set<Key, Hash, Pred, Alloc>& lhs,
+                    const unordered_set<Key, Hash, Pred, Alloc>& rhs)
     {
         return lhs.table_.is_eq_to(rhs.table_);
@@ -894,6 +894,6 @@
 
     template<class Key, class Hash, class Pred, class Alloc>
-    bool operator!=(unordered_set<Key, Hash, Pred, Alloc>& lhs,
-                    unordered_set<Key, Hash, Pred, Alloc>& rhs)
+    bool operator!=(const unordered_set<Key, Hash, Pred, Alloc>& lhs,
+                    const unordered_set<Key, Hash, Pred, Alloc>& rhs)
     {
         return !(lhs == rhs);
@@ -901,6 +901,6 @@
 
     template<class Key, class Hash, class Pred, class Alloc>
-    bool operator==(unordered_multiset<Key, Hash, Pred, Alloc>& lhs,
-                    unordered_multiset<Key, Hash, Pred, Alloc>& rhs)
+    bool operator==(const unordered_multiset<Key, Hash, Pred, Alloc>& lhs,
+                    const unordered_multiset<Key, Hash, Pred, Alloc>& rhs)
     {
         return lhs.table_.is_eq_to(rhs.table_);
@@ -908,6 +908,6 @@
 
     template<class Key, class Value, class Hash, class Pred, class Alloc>
-    bool operator!=(unordered_multiset<Key, Hash, Pred, Alloc>& lhs,
-                    unordered_multiset<Key, Hash, Pred, Alloc>& rhs)
+    bool operator!=(const unordered_multiset<Key, Hash, Pred, Alloc>& lhs,
+                    const unordered_multiset<Key, Hash, Pred, Alloc>& rhs)
     {
         return !(lhs == rhs);