diff --git a/bool.hpp b/bool.hpp
index 01a05c04..5afb510b 100644
--- a/bool.hpp
+++ b/bool.hpp
@@ -31,6 +31,10 @@ namespace cruft {
             : m_value (value::DONTCARE)
         { ; }
 
+        constexpr tribool ()
+            : tribool (nullptr)
+        { ; }
+
         /// Return true if the object contains a concrete value
         constexpr bool has (void) const
         {