diff --git a/fieldbasedtag.h b/fieldbasedtag.h
index dd75b6d..b18ad09 100644
--- a/fieldbasedtag.h
+++ b/fieldbasedtag.h
@@ -350,7 +350,7 @@ template <class ImplementationType> inline KnownField FieldMapBasedTag<Implement
 
 template <class ImplementationType> inline bool FieldMapBasedTag<ImplementationType>::supportsField(KnownField field) const
 {
-    static IdentifierType def;
+    static const auto def = IdentifierType();
     return fieldId(field) != def;
 }