diff --git a/src/main/java/org/codelibs/fess/es/client/FessEsClient.java b/src/main/java/org/codelibs/fess/es/client/FessEsClient.java
index 0fc09e702..40654e363 100644
--- a/src/main/java/org/codelibs/fess/es/client/FessEsClient.java
+++ b/src/main/java/org/codelibs/fess/es/client/FessEsClient.java
@@ -354,9 +354,13 @@ public class FessEsClient implements Client {
                 .replace("__SOURCE_INDEX__", fromIndex)//
                 .replace("__DEST_INDEX__", toIndex)
                 .replace("__SCRIPT_SOURCE__", ComponentUtil.getLanguageHelper().getReindexScriptSource());
-        try (CurlResponse response = ComponentUtil.getCurlHelper().post("/_reindex").param("refresh", fessConfig.getIndexReindexRefresh())
-                .param("requests_per_second", fessConfig.getIndexReindexRequestsPerSecond())
-                .param("scroll", fessConfig.getIndexReindexScroll()).param("max_docs", fessConfig.getIndexReindexMaxDocs())
+        final String refresh = StringUtil.isNotBlank(fessConfig.getIndexReindexRefresh()) ? fessConfig.getIndexReindexRefresh() : null;
+        final String requestsPerSecond =
+                StringUtil.isNotBlank(fessConfig.getIndexReindexRequestsPerSecond()) ? fessConfig.getIndexReindexRequestsPerSecond() : null;
+        final String scroll = StringUtil.isNotBlank(fessConfig.getIndexReindexScroll()) ? fessConfig.getIndexReindexScroll() : null;
+        final String maxDocs = StringUtil.isNotBlank(fessConfig.getIndexReindexMaxDocs()) ? fessConfig.getIndexReindexMaxDocs() : null;
+        try (CurlResponse response = ComponentUtil.getCurlHelper().post("/_reindex").param("refresh", refresh)
+                .param("requests_per_second", requestsPerSecond).param("scroll", scroll).param("max_docs", maxDocs)
                 .param("wait_for_completion", Boolean.toString(waitForCompletion)).body(source).execute()) {
             if (response.getHttpStatusCode() == 200) {
                 return true;
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 62987b5f1..0af65ddc6 100644
--- a/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
+++ b/src/main/java/org/codelibs/fess/mylasta/direction/FessConfig.java
@@ -732,7 +732,7 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
     /** The key of the configuration. e.g. 5m */
     String INDEX_REINDEX_SCROLL = "index.reindex.scroll";
 
-    /** The key of the configuration. e.g. -1 */
+    /** The key of the configuration. e.g.  */
     String INDEX_REINDEX_max_docs = "index.reindex.max_docs";
 
     /** The key of the configuration. e.g. 1000 */
@@ -3727,14 +3727,14 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
 
     /**
      * Get the value for the key 'index.reindex.max_docs'. <br>
-     * The value is, e.g. -1 <br>
+     * The value is, e.g.  <br>
      * @return The value of found property. (NotNull: if not found, exception but basically no way)
      */
     String getIndexReindexMaxDocs();
 
     /**
      * Get the value for the key 'index.reindex.max_docs' as {@link Integer}. <br>
-     * The value is, e.g. -1 <br>
+     * The value is, e.g.  <br>
      * @return The value of found property. (NotNull: if not found, exception but basically no way)
      * @throws NumberFormatException When the property is not integer.
      */
@@ -9904,7 +9904,7 @@ public interface FessConfig extends FessEnv, org.codelibs.fess.mylasta.direction
             defaultMap.put(FessConfig.INDEX_REINDEX_REFRESH, "false");
             defaultMap.put(FessConfig.INDEX_REINDEX_TIMEOUT, "1m");
             defaultMap.put(FessConfig.INDEX_REINDEX_SCROLL, "5m");
-            defaultMap.put(FessConfig.INDEX_REINDEX_max_docs, "-1");
+            defaultMap.put(FessConfig.INDEX_REINDEX_max_docs, "");
             defaultMap.put(FessConfig.QUERY_MAX_LENGTH, "1000");
             defaultMap.put(FessConfig.QUERY_TIMEOUT, "10000");
             defaultMap.put(FessConfig.QUERY_TIMEOUT_LOGGING, "true");
diff --git a/src/main/resources/fess_config.properties b/src/main/resources/fess_config.properties
index 8260b64d8..24c0b27fd 100644
--- a/src/main/resources/fess_config.properties
+++ b/src/main/resources/fess_config.properties
@@ -398,7 +398,7 @@ index.reindex.requests_per_second=-1
 index.reindex.refresh=false
 index.reindex.timeout=1m
 index.reindex.scroll=5m
-index.reindex.max_docs=-1
+index.reindex.max_docs=
 
 # query
 query.max.length=1000