diff -up ./lib/core/src/perl/RefHash.xs.orig ./lib/core/src/perl/RefHash.xs
--- ./lib/core/src/perl/RefHash.xs.orig	2015-08-10 13:59:14.436118422 -0400
+++ ./lib/core/src/perl/RefHash.xs	2015-08-10 13:59:59.358788890 -0400
@@ -88,7 +88,7 @@ SV* ref2key(SV *keysv, tmp_keysv *tmp_ke
    }                                                                    \
 } STMT_END
 
-static char err_ref[]="Reference as a key in a normal hash";
+static const char err_ref[]="Reference as a key in a normal hash";
 
 static inline
 int ref_key_allowed(HV* class)