diff --git a/HTMLparser.c b/HTMLparser.c
index 34df182b..00b64c13 100644
--- a/HTMLparser.c
+++ b/HTMLparser.c
@@ -4935,6 +4935,14 @@ htmlParseTryOrFinish(htmlParserCtxtPtr ctxt, int terminate) {
 		 */
 	        goto done;
             case XML_PARSER_START:
+                /*
+                 * Very first chars read from the document flow.
+                 */
+                if ((!terminate) && (avail < 4))
+                    goto done;
+
+                xmlDetectEncoding(ctxt);
+
                 /*
                  * This is wrong but matches long-standing behavior. In most
                  * cases, a document starting with an XML declaration will
@@ -4945,6 +4953,9 @@ htmlParseTryOrFinish(htmlParserCtxtPtr ctxt, int terminate) {
                     xmlSwitchEncoding(ctxt, XML_CHAR_ENCODING_UTF8);
                 }
 
+                /* fall through */
+
+            case XML_PARSER_XML_DECL:
                 if ((ctxt->sax) && (ctxt->sax->setDocumentLocator)) {
                     ctxt->sax->setDocumentLocator(ctxt->userData,
                             (xmlSAXLocator *) &xmlDefaultSAXLocator);
@@ -4953,8 +4964,9 @@ htmlParseTryOrFinish(htmlParserCtxtPtr ctxt, int terminate) {
 	            (!ctxt->disableSAX))
 		    ctxt->sax->startDocument(ctxt->userData);
 
-                /* Allow callback to modify state */
-                if (ctxt->instate == XML_PARSER_START)
+                /* Allow callback to modify state for tests */
+                if ((ctxt->instate == XML_PARSER_START) ||
+                    (ctxt->instate == XML_PARSER_XML_DECL))
                     ctxt->instate = XML_PARSER_MISC;
 		break;
             case XML_PARSER_START_TAG: {
diff --git a/runtest.c b/runtest.c
index d06ec83e..f6bb9679 100644
--- a/runtest.c
+++ b/runtest.c
@@ -1797,6 +1797,8 @@ htmlTokenizerTest(const char *filename, const char *result,
         config.startTag = BAD_CAST startTag;
         config.inCharacters = 0;
         ctxt->_private = &config;
+        /* Skip charset auto-detection */
+        ctxt->instate = XML_PARSER_XML_DECL;
         htmlCtxtUseOptions(ctxt, options | HTML_PARSE_HTML5);
         htmlParseChunk(ctxt, data, size, 1);
         htmlFreeParserCtxt(ctxt);