diff --git a/include/boost/unordered/detail/implementation.hpp b/include/boost/unordered/detail/implementation.hpp
index 5daf53ee..1352d462 100644
--- a/include/boost/unordered/detail/implementation.hpp
+++ b/include/boost/unordered/detail/implementation.hpp
@@ -827,13 +827,13 @@ namespace boost {
         T* operator->() { return value_.value_ptr(); }
         T const* operator->() const { return value_.value_ptr(); }
 
-        bool operator==(optional<T> const& x)
+        bool operator==(optional<T> const& x) const
         {
           return has_value_ ? x.has_value_ && value_.value() == x.value_.value()
                             : !x.has_value_;
         }
 
-        bool operator!=(optional<T> const& x) { return !((*this) == x); }
+        bool operator!=(optional<T> const& x) const { return !((*this) == x); }
 
         void swap(optional<T>& x)
         {
diff --git a/test/helpers/list.hpp b/test/helpers/list.hpp
index d39c766e..3fddd6d3 100644
--- a/test/helpers/list.hpp
+++ b/test/helpers/list.hpp
@@ -113,6 +113,10 @@ namespace test {
         ptr_ = ptr_->next_;
         return tmp;
       }
+
+      bool operator==(list_iterator y) const { return ptr_ == y.ptr_; }
+      bool operator!=(list_iterator y) const { return ptr_ != y.ptr_; }
+
       bool operator==(const_iterator y) const { return ptr_ == y.ptr_; }
       bool operator!=(const_iterator y) const { return ptr_ != y.ptr_; }
     };
diff --git a/test/unordered/allocator_traits.cpp b/test/unordered/allocator_traits.cpp
index 476205b7..0517fb97 100644
--- a/test/unordered/allocator_traits.cpp
+++ b/test/unordered/allocator_traits.cpp
@@ -65,9 +65,9 @@
   {                                                                            \
     return (std::numeric_limits<size_type>::max)();                            \
   }                                                                            \
-  bool operator==(name<T> const&) { return true; }                             \
-  bool operator!=(name<T> const&) { return false; }                            \
-/**/
+  bool operator==(name<T> const&) const { return true; }                       \
+  bool operator!=(name<T> const&) const { return false; }                      \
+  /**/
 
 struct yes_type
 {
diff --git a/test/unordered/deduction_tests.cpp b/test/unordered/deduction_tests.cpp
index 673c0609..cffb0c1d 100644
--- a/test/unordered/deduction_tests.cpp
+++ b/test/unordered/deduction_tests.cpp
@@ -30,8 +30,8 @@ template <typename T> struct test_allocator
   template <typename T2> test_allocator(test_allocator<T2> const&) {}
   T* allocate(std::size_t n) const { return (T*)malloc(sizeof(T) * n); }
   void deallocate(T* ptr, std::size_t) const { free(ptr); }
-  bool operator==(test_allocator const&) { return true; }
-  bool operator!=(test_allocator const&) { return false; }
+  bool operator==(test_allocator const&) const { return true; }
+  bool operator!=(test_allocator const&) const { return false; }
 };
 #endif