diff --git a/Makefile b/Makefile
index ea0754fa5..cb6eeb573 100644
--- a/Makefile
+++ b/Makefile
@@ -98,7 +98,7 @@ ifdef HOST_WINDOWS
   GLOBAL_LDFLAGS += -Wl,--export-all-symbols
 endif
 
-GLOBAL_CXXFLAGS += -g -Wall -Wimplicit-fallthrough -include $(buildprefix)config.h -std=c++2a -I src
+GLOBAL_CXXFLAGS += -g -Wall -Wdeprecated-copy -Wimplicit-fallthrough -include $(buildprefix)config.h -std=c++2a -I src
 
 # Include the main lib, causing rules to be defined
 
diff --git a/src/libutil/fmt.hh b/src/libutil/fmt.hh
index c178257d4..ef44a8409 100644
--- a/src/libutil/fmt.hh
+++ b/src/libutil/fmt.hh
@@ -182,6 +182,8 @@ public:
         return *this;
     }
 
+    HintFmt & operator=(HintFmt const & rhs) = default;
+
     std::string str() const
     {
         return fmt.str();
diff --git a/src/libutil/ref.hh b/src/libutil/ref.hh
index 5d0c3696d..03aa64273 100644
--- a/src/libutil/ref.hh
+++ b/src/libutil/ref.hh
@@ -77,6 +77,8 @@ public:
         return ref<T2>((std::shared_ptr<T2>) p);
     }
 
+    ref<T> & operator=(ref<T> const & rhs) = default;
+
     bool operator == (const ref<T> & other) const
     {
         return p == other.p;