diff --git a/core/cont/src/TClassTable.cxx b/core/cont/src/TClassTable.cxx
index f6738decf936fb8f532ecc964c3159972d0f80d1..3008f1b52360afccc3ee4ecd65a6250d40712167 100644
--- a/core/cont/src/TClassTable.cxx
+++ b/core/cont/src/TClassTable.cxx
@@ -195,7 +195,7 @@ namespace ROOT {
 
    static UInt_t ClassTableHash(const char *name, UInt_t size)
    {
-      const char *p = name;
+      auto p = reinterpret_cast<const unsigned char*>( name );
       UInt_t slot = 0;
 
       while (*p) slot = slot<<1 ^ *p++;