diff --git a/core-it-suite/src/test/java/org/apache/maven/it/IntegrationTestSuite.java b/core-it-suite/src/test/java/org/apache/maven/it/IntegrationTestSuite.java
index 9dcef0b..8e9f24c 100644
--- a/core-it-suite/src/test/java/org/apache/maven/it/IntegrationTestSuite.java
+++ b/core-it-suite/src/test/java/org/apache/maven/it/IntegrationTestSuite.java
@@ -106,6 +106,7 @@
         // -------------------------------------------------------------------------------------------------------------
         // suite.addTestSuite( MavenIT0108SnapshotUpdateTest.class ); -- MNG-3137
 
+        suite.addTestSuite( MavenITmng6401InterpolateSettingsXmlTest.class);
         suite.addTestSuite( MavenITmng6386BaseUriPropertyTest.class );
         suite.addTestSuite( MavenITmng6330RelativePath.class );
         suite.addTestSuite( MavenITmng6240PluginExtensionAetherProvider.class );
diff --git a/core-it-suite/src/test/java/org/apache/maven/it/MavenITmng6401InterpolateSettingsXmlTest.java b/core-it-suite/src/test/java/org/apache/maven/it/MavenITmng6401InterpolateSettingsXmlTest.java
new file mode 100644
index 0000000..4307216
--- /dev/null
+++ b/core-it-suite/src/test/java/org/apache/maven/it/MavenITmng6401InterpolateSettingsXmlTest.java
@@ -0,0 +1,43 @@
+package org.apache.maven.it;
+
+import java.io.File;
+import java.util.Properties;
+
+import org.apache.maven.it.util.ResourceExtractor;
+
+/**
+ * This is a test set for <a href="https://issues.apache.org/jira/browse/MNG-6401">MNG-6401</a>:
+ * check interpolation for various types fields in settings.xml.
+ */
+public class MavenITmng6401InterpolateSettingsXmlTest
+    extends AbstractMavenIntegrationTestCase
+{
+
+    public MavenITmng6401InterpolateSettingsXmlTest()
+    {
+        super( "[3.5.4,)" );
+    }
+
+    public void testInterpolateSettingsXml()
+        throws Exception
+    {
+        File testDir = ResourceExtractor.simpleExtractResources( getClass(), "/mng-6401" );
+
+        Verifier verifier = newVerifier( testDir.getAbsolutePath() );
+        verifier.addCliOption( "--settings" );
+        verifier.addCliOption( "settings.xml" );
+        verifier.setEnvironmentVariable("MAVEN_PROXY_ACTIVE_BOOLEAN", "true");
+        verifier.setEnvironmentVariable("MAVEN_PROXY_HOST_STRING", "myproxy.host.net");
+        verifier.setEnvironmentVariable("MAVEN_PROXY_PORT_INT", "18080");
+        verifier.executeGoal( "validate" );
+
+        verifier.verifyErrorFreeLog();
+        verifier.resetStreams();
+
+        Properties props = verifier.loadProperties( "target/settings.properties" );
+        assertEquals( "true", props.getProperty( "settings.proxies.0.active" ) );
+        assertEquals( "myproxy.host.net", props.getProperty( "settings.proxies.0.host" ) );
+        assertEquals( "18080", props.getProperty( "settings.proxies.0.port" ) );
+    }
+}
+
diff --git a/core-it-suite/src/test/resources/mng-6401/pom.xml b/core-it-suite/src/test/resources/mng-6401/pom.xml
new file mode 100644
index 0000000..76358d7
--- /dev/null
+++ b/core-it-suite/src/test/resources/mng-6401/pom.xml
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<project>
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.apache.maven.its.mng6401</groupId>
+  <artifactId>test</artifactId>
+  <version>1.0.0-SNAPSHOT</version>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.its.plugins</groupId>
+        <artifactId>maven-it-plugin-expression</artifactId>
+        <version>2.1-SNAPSHOT</version>
+        <configuration>
+          <outputFile>target/settings.properties</outputFile>
+          <expressions>
+            <expression>settings/proxies/0/active</expression>
+            <expression>settings/proxies/0/host</expression>
+            <expression>settings/proxies/0/port</expression>
+          </expressions>
+        </configuration>
+        <executions>
+          <execution>
+            <id>test</id>
+            <phase>validate</phase>
+            <goals>
+              <goal>eval</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+</project>
diff --git a/core-it-suite/src/test/resources/mng-6401/settings.xml b/core-it-suite/src/test/resources/mng-6401/settings.xml
new file mode 100644
index 0000000..b0a01e4
--- /dev/null
+++ b/core-it-suite/src/test/resources/mng-6401/settings.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<settings>
+  <proxies>
+    <proxy>
+      <id>my_proxy</id>
+      <active>${env.MAVEN_PROXY_ACTIVE_BOOLEAN}</active>
+      <protocol>http</protocol>
+      <host>${env.MAVEN_PROXY_HOST_STRING}</host>
+      <port>${env.MAVEN_PROXY_PORT_INT}</port>
+      <nonProxyHosts>local.net|some.host.com</nonProxyHosts>
+    </proxy>
+  </proxies>
+</settings>