diff --git a/xml/relaxng/src/resources/html5-schema/embed-ext.rnc b/xml/relaxng/src/resources/html5-schema/embed-ext.rnc
new file mode 100644
index 000000000000..9b153c64f339
--- /dev/null
+++ b/xml/relaxng/src/resources/html5-schema/embed-ext.rnc
@@ -0,0 +1,3 @@
+datatypes w = "http://whattf.org/datatype-draft"
+
+embed.attrs |= common.attr.anything
\ No newline at end of file
diff --git a/xml/relaxng/src/resources/html5-schema/html5.rnc b/xml/relaxng/src/resources/html5-schema/html5.rnc
index 4d0a71a75a46..5a2baec353ef 100644
--- a/xml/relaxng/src/resources/html5-schema/html5.rnc
+++ b/xml/relaxng/src/resources/html5-schema/html5.rnc
@@ -48,6 +48,7 @@ include "sectional.rnc"
 include "structural.rnc"
 include "revision.rnc"
 include "embed.rnc"
+include "embed-ext.rnc"
 include "ruby.rnc"
 include "media.rnc"
 include "core-scripting.rnc"
diff --git a/xml/relaxng/src/resources/html5-schema/xhtml5.rnc b/xml/relaxng/src/resources/html5-schema/xhtml5.rnc
index 2d17f9f8e259..043b70ef87e0 100644
--- a/xml/relaxng/src/resources/html5-schema/xhtml5.rnc
+++ b/xml/relaxng/src/resources/html5-schema/xhtml5.rnc
@@ -32,6 +32,7 @@ include "sectional.rnc"
 include "structural.rnc"
 include "revision.rnc"
 include "embed.rnc"
+include "embed-ext.rnc"
 include "ruby.rnc"
 include "media.rnc"
 include "core-scripting.rnc"
diff --git a/xml/xml-psi-impl/src/com/intellij/psi/impl/source/html/dtd/HtmlElementDescriptorImpl.java b/xml/xml-psi-impl/src/com/intellij/psi/impl/source/html/dtd/HtmlElementDescriptorImpl.java
index 2dd7767f435f..bd9085a50b42 100644
--- a/xml/xml-psi-impl/src/com/intellij/psi/impl/source/html/dtd/HtmlElementDescriptorImpl.java
+++ b/xml/xml-psi-impl/src/com/intellij/psi/impl/source/html/dtd/HtmlElementDescriptorImpl.java
@@ -23,6 +23,7 @@ import com.intellij.xml.XmlElementDescriptor;
 import com.intellij.xml.XmlNSDescriptor;
 import com.intellij.xml.impl.dtd.BaseXmlElementDescriptorImpl;
 import com.intellij.xml.impl.schema.XmlNSDescriptorImpl;
+import com.intellij.xml.util.HtmlUtil;
 import com.intellij.xml.util.XmlUtil;
 
 import java.util.HashMap;
@@ -110,6 +111,9 @@ public class HtmlElementDescriptorImpl extends BaseXmlElementDescriptorImpl {
         }
       }
     }
+    if (descriptor == null && HtmlUtil.isHtml5Context(context)) {
+      descriptor = myDelegate.getAttributeDescriptor(attributeName, context);
+    }
     return descriptor;
   }