diff --git a/src/main/java/io/github/gitbucket/markedj/Grammer.java b/src/main/java/io/github/gitbucket/markedj/Grammer.java
index 2c33b2b..bceae35 100644
--- a/src/main/java/io/github/gitbucket/markedj/Grammer.java
+++ b/src/main/java/io/github/gitbucket/markedj/Grammer.java
@@ -12,7 +12,7 @@ public class Grammer {
 
     public static String BULLET            = "(?:[*+-]|\\d+\\.)";
     public static String COMMENT           = "<!--[\\s\\S]*?-->";
-    public static String TAG               = "(?!(?:a|em|strong|small|s|cite|q|dfn|abbr|data|time|code|var|samp|kbd|sub|sup|i|b|u|mark|ruby|rt|rp|bdi|bdo|span|br|wbr|ins|del|img)\\b)\\w+(?!:/|[^\\w\\s@]*@)\\b";
+    public static String TAG               = "(?!(?:a|em|strong|small|s|cite|q|dfn|abbr|data|time|code|var|samp|kbd|sub|sup|i|b|u|mark|ruby|rt|rp|bdi|bdo|span|br|wbr|ins|del|img)\\b|details|summary)\\w+(?!:/|[^\\w\\s@]*@)\\b";
     public static String CLOSED            = "<(" + TAG + ")[\\s\\S]+?<\\/\\1>";
     public static String CLOSING           = "<" + TAG + "(?:\"[^\"]*\"|'[^']*'|[^'\">])*?>";
     public static String HR                = "\\n+(?=\\1?(?:[-*_] *){3,}(?:\\n+|$))";
diff --git a/src/test/java/io/github/gitbucket/markedj/MarkedTest.java b/src/test/java/io/github/gitbucket/markedj/MarkedTest.java
index a6ce24c..de56ed0 100644
--- a/src/test/java/io/github/gitbucket/markedj/MarkedTest.java
+++ b/src/test/java/io/github/gitbucket/markedj/MarkedTest.java
@@ -204,6 +204,22 @@ public void testEmptyTableCell() throws Exception {
                         "</table>\n", result);
     }
 
+    @Test
+    public void testDetailsTag() throws Exception {
+        String result = Marked.marked(
+		"<details>\n" +
+		"<summary>sample title<summary>\n" +
+		"long long text\n" +
+		"</details>\n");
+
+	assertEquals(
+		"<p><details>\n" +
+		"<summary>sample title<summary>\n" +
+		"long long text\n" +
+		"</details></p>\n",
+		result);
+    }
+
     private String loadResourceAsString(String path) throws IOException {
         InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream(path);
         try {