diff --git a/src/main/java/org/codelibs/fess/Constants.java b/src/main/java/org/codelibs/fess/Constants.java
index f534a1a40..2e1e3ec9d 100644
--- a/src/main/java/org/codelibs/fess/Constants.java
+++ b/src/main/java/org/codelibs/fess/Constants.java
@@ -445,4 +445,8 @@ public class Constants extends CoreLibConstants {
     public static final String TRACK_TOTAL_HITS = "track_total_hits";
 
     public static final String SYSTEM_PROP_PREFIX = "fess.system.";
+
+    public static final String XERCES_FEATURE_PREFIX = "http://apache.org/xml/features/";
+
+    public static final String LOAD_EXTERNAL_DTD_FEATURE = "nonvalidating/load-external-dtd";
 }
diff --git a/src/main/java/org/codelibs/fess/ds/DataStoreFactory.java b/src/main/java/org/codelibs/fess/ds/DataStoreFactory.java
index 21aa84637..83cde864a 100644
--- a/src/main/java/org/codelibs/fess/ds/DataStoreFactory.java
+++ b/src/main/java/org/codelibs/fess/ds/DataStoreFactory.java
@@ -34,8 +34,8 @@ import javax.xml.parsers.DocumentBuilderFactory;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.apache.xerces.impl.Constants;
 import org.codelibs.core.lang.StringUtil;
+import org.codelibs.fess.Constants;
 import org.codelibs.fess.helper.PluginHelper;
 import org.codelibs.fess.util.ResourceUtil;
 import org.w3c.dom.Document;