diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5995b07..e92fa91 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -116,6 +116,6 @@ if (PHMAP_BUILD_EXAMPLES)
     add_executable(ex_hash_std examples/hash_std.cc)
     add_executable(ex_two_files examples/f1.cc examples/f2.cc)
     add_executable(ex_insert_bench examples/insert_bench.cc)
+    add_executable(ex_knucleotide examples/knucleotide.cc)
 endif()
 
-
diff --git a/parallel_hashmap/phmap_base.h b/parallel_hashmap/phmap_base.h
index 9d897c3..94d780b 100644
--- a/parallel_hashmap/phmap_base.h
+++ b/parallel_hashmap/phmap_base.h
@@ -4580,8 +4580,8 @@ public:
         DoNothing(Mutex&, phmap::adopt_lock_t) noexcept {}
         DoNothing(Mutex&, phmap::defer_lock_t) noexcept {}
         DoNothing(Mutex&, phmap::try_to_lock_t) {}
-        template<class T> explicit DoNothing(T&) {}
         template<class T> explicit DoNothing(T&&) {}
+        DoNothing& operator=(const DoNothing&) { return *this; }
         DoNothing& operator=(DoNothing&&) { return *this; }
         void swap(DoNothing &) {}
         bool owns_lock() const noexcept { return true; }