diff --git a/java/src/org/openqa/selenium/remote/http/HttpMessage.java b/java/src/org/openqa/selenium/remote/http/HttpMessage.java
index d8ec4129d4da7..8d388c8de0084 100644
--- a/java/src/org/openqa/selenium/remote/http/HttpMessage.java
+++ b/java/src/org/openqa/selenium/remote/http/HttpMessage.java
@@ -123,7 +123,7 @@ public String getHeader(String name) {
    * @return self
    */
   public M setHeader(String name, String value) {
-    return removeHeader(name).addHeader(name, value);
+    return removeHeader(name.toLowerCase()).addHeader(name.toLowerCase(), value);
   }
 
   /**
@@ -135,7 +135,7 @@ public M setHeader(String name, String value) {
    * @return self
    */
   public M addHeader(String name, String value) {
-    headers.computeIfAbsent(name, (n) -> new ArrayList<>()).add(value);
+    headers.computeIfAbsent(name.toLowerCase(), (n) -> new ArrayList<>()).add(value);
     return self();
   }
 
diff --git a/java/test/org/openqa/selenium/devtools/ChangeUserAgentTest.java b/java/test/org/openqa/selenium/devtools/ChangeUserAgentTest.java
index 1572fdc6012dd..e2c6284202b15 100644
--- a/java/test/org/openqa/selenium/devtools/ChangeUserAgentTest.java
+++ b/java/test/org/openqa/selenium/devtools/ChangeUserAgentTest.java
@@ -48,8 +48,8 @@ public void canChangeUserAgent() {
             .collect(
                 Collectors.toMap(cells -> cells.get(0).getText(), cells -> cells.get(1).getText()));
     assertThat(headers)
-        .containsEntry("User-Agent", "Camembert 1.0")
-        .containsEntry("Accept-Language", "da, en-gb;q=0.9, *;q=0.8");
+        .containsEntry("user-agent", "Camembert 1.0")
+        .containsEntry("accept-language", "da, en-gb;q=0.9, *;q=0.8");
 
     Object platform =
         ((JavascriptExecutor) driver).executeScript("return window.navigator.platform");
diff --git a/java/test/org/openqa/selenium/remote/http/DumpHttpExchangeFilterTest.java b/java/test/org/openqa/selenium/remote/http/DumpHttpExchangeFilterTest.java
index ef0bb301db21d..9b068d837c175 100644
--- a/java/test/org/openqa/selenium/remote/http/DumpHttpExchangeFilterTest.java
+++ b/java/test/org/openqa/selenium/remote/http/DumpHttpExchangeFilterTest.java
@@ -34,7 +34,7 @@ void shouldIncludeRequestAndResponseHeaders() {
         dumpFilter.requestLogMessage(
             new HttpRequest(GET, "/foo").addHeader("Peas", "and Sausages"));
 
-    assertThat(reqLog).contains("Peas");
+    assertThat(reqLog).contains("peas");
     assertThat(reqLog).contains("and Sausages");
 
     String resLog =
@@ -43,7 +43,7 @@ void shouldIncludeRequestAndResponseHeaders() {
                 .addHeader("Cheese", "Brie")
                 .setContent(string("Hello, World!", UTF_8)));
 
-    assertThat(resLog).contains("Cheese");
+    assertThat(resLog).contains("cheese");
     assertThat(resLog).contains("Brie");
   }
 
diff --git a/java/test/org/openqa/selenium/remote/http/HttpMessageTest.java b/java/test/org/openqa/selenium/remote/http/HttpMessageTest.java
index 61ee108494749..f29876cc78b0c 100644
--- a/java/test/org/openqa/selenium/remote/http/HttpMessageTest.java
+++ b/java/test/org/openqa/selenium/remote/http/HttpMessageTest.java
@@ -40,8 +40,8 @@ void allHeadersAreAdded() {
 
       message.getHeaderNames().forEach(headers::add);
 
-      assertThat(headers.contains("Content-Length")).isTrue();
-      assertThat(headers.contains("Content-length")).isTrue();
+      assertThat(headers.contains("Content-Length")).isFalse();
+      assertThat(headers.contains("Content-length")).isFalse();
       assertThat(headers.contains("content-length")).isTrue();
     }
   }
@@ -54,7 +54,7 @@ void readingIsCaseInsensitive() {
       message.addHeader("Content-length", "2048");
       message.addHeader("content-length", "4096");
 
-      assertThat(message.getHeader("Content-Length")).isEqualTo("4096");
+      assertThat(message.getHeader("Content-Length")).isEqualTo("1024");
     }
   }
 
@@ -74,7 +74,8 @@ void replacingIsCaseInsensitive() {
       assertThat(message.getHeader("content-length")).isEqualTo("8192");
       assertThat(headers.contains("Content-Length")).isFalse();
       assertThat(headers.contains("Content-length")).isFalse();
-      assertThat(headers.contains("content-length")).isFalse();
+      assertThat(headers.contains("contenT-length")).isFalse();
+      assertThat(headers.contains("content-length")).isTrue();
     }
   }