diff --git a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderHandler.java b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderHandler.java
index 0b3a8bedd8..61e825d02b 100644
--- a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderHandler.java
+++ b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderHandler.java
@@ -62,8 +62,8 @@ public class HostHeaderHandler extends ScopedHandler {
         // Different from customizer -- empty is ok here
         validHosts.add("");
         try {
-            validHosts.add(InetAddress.getLocalHost().getHostName());
-            validHosts.add(InetAddress.getLocalHost().getHostName() + ":" + serverPort);
+            validHosts.add(InetAddress.getLocalHost().getHostName().toLowerCase());
+            validHosts.add(InetAddress.getLocalHost().getHostName().toLowerCase() + ":" + serverPort);
         } catch (final Exception e) {
             logger.warn("Failed to determine local hostname.", e);
         }
diff --git a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderSanitizationCustomizer.java b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderSanitizationCustomizer.java
index 5a10610246..3a7b22b2e9 100644
--- a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderSanitizationCustomizer.java
+++ b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-web/nifi-jetty/src/main/java/org/apache/nifi/web/server/HostHeaderSanitizationCustomizer.java
@@ -55,8 +55,8 @@ public class HostHeaderSanitizationCustomizer implements HttpConfiguration.Custo
         validHosts.add("localhost");
         validHosts.add("localhost:" + serverPort);
         try {
-            validHosts.add(InetAddress.getLocalHost().getHostName());
-            validHosts.add(InetAddress.getLocalHost().getHostName() + ":" + serverPort);
+            validHosts.add(InetAddress.getLocalHost().getHostName().toLowerCase());
+            validHosts.add(InetAddress.getLocalHost().getHostName().toLowerCase() + ":" + serverPort);
         } catch (final Exception e) {
             logger.warn("Failed to determine local hostname.", e);
         }