diff --git a/expat/xmltok/xmltok_impl.c b/expat/xmltok/xmltok_impl.c
index 0361b261..8f8ffc44 100755
--- a/expat/xmltok/xmltok_impl.c
+++ b/expat/xmltok/xmltok_impl.c
@@ -1164,6 +1164,11 @@ int PREFIX(isPublicId)(const ENCODING *enc, const char *ptr, const char *end,
     case BT_QUEST:
     case BT_CR:
     case BT_LF:
+    case BT_SEMI:
+    case BT_EXCL:
+    case BT_AST:
+    case BT_PERCNT:
+    case BT_NUM:
       break;
     case BT_S:
       if (CHAR_MATCHES(enc, ptr, '\t')) {
@@ -1173,12 +1178,18 @@ int PREFIX(isPublicId)(const ENCODING *enc, const char *ptr, const char *end,
       break;
     case BT_NAME:
     case BT_NMSTRT:
-      if (!(BYTE_TO_ASCII(enc, ptr) & ~0x7f)
-	  && !CHAR_MATCHES(enc, ptr, '_'))
+      if (!(BYTE_TO_ASCII(enc, ptr) & ~0x7f))
 	break;
     default:
-      *badPtr = ptr;
-      return 0;
+      switch (BYTE_TO_ASCII(enc, ptr)) {
+      case 0x24: /* $ */
+      case 0x40: /* @ */
+	break;
+      default:
+	*badPtr = ptr;
+	return 0;
+      }
+      break;
     }
   }
   return 1;