diff --git a/src/main/java/org/codelibs/fess/api/gsa/GsaApiManager.java b/src/main/java/org/codelibs/fess/api/gsa/GsaApiManager.java
index 210098522..f121fd4b1 100644
--- a/src/main/java/org/codelibs/fess/api/gsa/GsaApiManager.java
+++ b/src/main/java/org/codelibs/fess/api/gsa/GsaApiManager.java
@@ -66,17 +66,8 @@ public class GsaApiManager extends BaseApiManager implements WebApiManager {
     private static final String OUTPUT_XML = "xml"; // or xml_no_dtd
     // http://www.google.com/google.dtd.
 
-    @Deprecated
-    private static final String GSA_META_SUFFIX = "_s";
-
     protected String gsaPathPrefix = "/gsa";
 
-    protected String gsaMetaPrefix = "MT_";
-
-    protected String charsetField = "charset";
-
-    protected String contentTypeField = "content_type";
-
     @PostConstruct
     public void register() {
         if (logger.isInfoEnabled()) {
@@ -254,13 +245,12 @@ public class GsaApiManager extends BaseApiManager implements WebApiManager {
                         document.put("LANG", lang);
                         document.remove(fessConfig.getIndexFieldLang());
                     }
+                    final String gsaMetaPrefix = fessConfig.getQueryGsaMetaPrefix();
                     for (final Map.Entry<String, Object> entry : document.entrySet()) {
                         final String name = entry.getKey();
                         if (StringUtil.isNotBlank(name) && entry.getValue() != null && fessConfig.isGsaResponseFields(name)) {
                             if (name.startsWith(gsaMetaPrefix)) {
-                                final String tagName =
-                                        name.replaceFirst("^" + gsaMetaPrefix, StringUtil.EMPTY).replaceAll(GSA_META_SUFFIX + "\\z",
-                                                StringUtil.EMPTY);
+                                final String tagName = name.replaceFirst("^" + gsaMetaPrefix, StringUtil.EMPTY);
                                 if (getFields.contains(tagName)) {
                                     buf.append("<MT N=\"");
                                     buf.append(tagName);
@@ -298,9 +288,11 @@ public class GsaApiManager extends BaseApiManager implements WebApiManager {
                     buf.append(DocumentUtil.getValue(document, fessConfig.getIndexFieldDocId(), String.class));
                     document.remove(fessConfig.getIndexFieldDocId());
                     buf.append("\" ENC=\"");
+                    final String charsetField = fessConfig.getQueryGsaIndexFieldCharset();
                     String charset = DocumentUtil.getValue(document, charsetField, String.class);
                     document.remove(charsetField);
                     if (StringUtil.isBlank(charset)) {
+                        final String contentTypeField = fessConfig.getQueryGsaIndexFieldContentType();
                         charset = DocumentUtil.getValue(document, contentTypeField, String.class);
                         document.remove(contentTypeField);
                         if (StringUtil.isNotBlank(charset)) {
@@ -434,7 +426,7 @@ public class GsaApiManager extends BaseApiManager implements WebApiManager {
         }
     }
 
-    protected class GsaRequestParams extends SearchRequestParams {
+    protected static class GsaRequestParams extends SearchRequestParams {
 
         private final HttpServletRequest request;
 
@@ -466,6 +458,7 @@ public class GsaApiManager extends BaseApiManager implements WebApiManager {
             for (final String s : getParamValueArray(request, "ex_q")) {
                 queryList.add(s.trim());
             }
+            final String gsaMetaPrefix = fessConfig.getQueryGsaMetaPrefix();
             final String requiredFields = request.getParameter("requiredfields");
             if (StringUtil.isNotBlank(requiredFields)) {
                 queryList.add(gsaMetaPrefix + requiredFields.replace(".", " AND " + gsaMetaPrefix).replace("|", " OR " + gsaMetaPrefix));
@@ -641,18 +634,6 @@ public class GsaApiManager extends BaseApiManager implements WebApiManager {
         this.gsaPathPrefix = gsaPathPrefix;
     }
 
-    public void setGsaMetaPrefix(final String gsaMetaPrefix) {
-        this.gsaMetaPrefix = gsaMetaPrefix;
-    }
-
-    public void setCharsetField(final String charsetField) {
-        this.charsetField = charsetField;
-    }
-
-    public void setContentTypeField(final String contentTypeField) {
-        this.contentTypeField = contentTypeField;
-    }
-
     @Override
     protected void writeHeaders(final HttpServletResponse response) {
         ComponentUtil.getFessConfig().getApiGsaResponseHeaderList().forEach(e -> response.setHeader(e.getFirst(), e.getSecond()));
diff --git a/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java b/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
index bd4b2aaeb..2cb88f2fa 100644
--- a/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
+++ b/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
@@ -699,6 +699,15 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
     /** The key of the configuration. e.g.  */
     String QUERY_GSA_DEFAULT_SORT = "query.gsa.default.sort";
 
+    /** The key of the configuration. e.g. MT_ */
+    String QUERY_GSA_META_PREFIX = "query.gsa.meta.prefix";
+
+    /** The key of the configuration. e.g. charset */
+    String QUERY_GSA_INDEX_FIELD_CHARSET = "query.gsa.index.field.charset";
+
+    /** The key of the configuration. e.g. content_type */
+    String QUERY_GSA_INDEX_FIELD_content_type_ = "query.gsa.index.field.content_type.";
+
     /** The key of the configuration. e.g. 4 */
     String QUERY_COLLAPSE_MAX_CONCURRENT_GROUP_RESULTS = "query.collapse.max.concurrent.group.results";
 
@@ -3545,6 +3554,27 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
      */
     Integer getQueryGsaDefaultSortAsInteger();
 
+    /**
+     * Get the value for the key 'query.gsa.meta.prefix'. <br>
+     * The value is, e.g. MT_ <br>
+     * @return The value of found property. (NotNull: if not found, exception but basically no way)
+     */
+    String getQueryGsaMetaPrefix();
+
+    /**
+     * Get the value for the key 'query.gsa.index.field.charset'. <br>
+     * The value is, e.g. charset <br>
+     * @return The value of found property. (NotNull: if not found, exception but basically no way)
+     */
+    String getQueryGsaIndexFieldCharset();
+
+    /**
+     * Get the value for the key 'query.gsa.index.field.content_type.'. <br>
+     * The value is, e.g. content_type <br>
+     * @return The value of found property. (NotNull: if not found, exception but basically no way)
+     */
+    String getQueryGsaIndexFieldContentType();
+
     /**
      * Get the value for the key 'query.collapse.max.concurrent.group.results'. <br>
      * The value is, e.g. 4 <br>
@@ -6990,6 +7020,18 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
             return getAsInteger(FessConfig.QUERY_GSA_DEFAULT_SORT);
         }
 
+        public String getQueryGsaMetaPrefix() {
+            return get(FessConfig.QUERY_GSA_META_PREFIX);
+        }
+
+        public String getQueryGsaIndexFieldCharset() {
+            return get(FessConfig.QUERY_GSA_INDEX_FIELD_CHARSET);
+        }
+
+        public String getQueryGsaIndexFieldContentType() {
+            return get(FessConfig.QUERY_GSA_INDEX_FIELD_content_type_);
+        }
+
         public String getQueryCollapseMaxConcurrentGroupResults() {
             return get(FessConfig.QUERY_COLLAPSE_MAX_CONCURRENT_GROUP_RESULTS);
         }
@@ -8429,6 +8471,9 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
             defaultMap.put(FessConfig.QUERY_GSA_RESPONSE_FIELDS, "UE,U,T,RK,S,LANG");
             defaultMap.put(FessConfig.QUERY_GSA_DEFAULT_LANG, "en");
             defaultMap.put(FessConfig.QUERY_GSA_DEFAULT_SORT, "");
+            defaultMap.put(FessConfig.QUERY_GSA_META_PREFIX, "MT_");
+            defaultMap.put(FessConfig.QUERY_GSA_INDEX_FIELD_CHARSET, "charset");
+            defaultMap.put(FessConfig.QUERY_GSA_INDEX_FIELD_content_type_, "content_type");
             defaultMap.put(FessConfig.QUERY_COLLAPSE_MAX_CONCURRENT_GROUP_RESULTS, "4");
             defaultMap.put(FessConfig.QUERY_COLLAPSE_INNER_HITS_NAME, "similar_docs");
             defaultMap.put(FessConfig.QUERY_COLLAPSE_INNER_HITS_SIZE, "0");
diff --git a/src/main/resources/fess_config.properties b/src/main/resources/fess_config.properties
index 354ee33a1..e11843fae 100644
--- a/src/main/resources/fess_config.properties
+++ b/src/main/resources/fess_config.properties
@@ -338,6 +338,9 @@ query.additional.not.analyzed.fields=
 query.gsa.response.fields=UE,U,T,RK,S,LANG
 query.gsa.default.lang=en
 query.gsa.default.sort=
+query.gsa.meta.prefix=MT_
+query.gsa.index.field.charset=charset
+query.gsa.index.field.content_type.=content_type
 query.collapse.max.concurrent.group.results=4
 query.collapse.inner.hits.name=similar_docs
 query.collapse.inner.hits.size=0