--- a/src/ov.h
+++ b/src/ov.h
@@ -303,8 +303,7 @@
       if (rep->count > 1)
 	{
 	  --rep->count;
-	  rep = rep->clone ();
-	  rep->count = 1;
+	  rep = rep->unique_clone ();
 	}
     }
 
@@ -316,8 +315,7 @@
       if (rep->count > obsolete_copies + 1)
 	{
 	  --rep->count;
-	  rep = rep->clone ();
-	  rep->count = 1;
+	  rep = rep->unique_clone ();
 	}
     }
 
@@ -1142,6 +1140,10 @@
 
   binary_op op_eq_to_binary_op (assign_op op);
 
+  // This declaration protects against constructing octave_value from
+  // const octave_base_value* which actually silently calls octave_value (bool).
+  octave_value (const octave_base_value *);
+
   DECLARE_OCTAVE_ALLOCATOR
 };