diff --git a/jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/HttpParser.java b/jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/HttpParser.java
index 810c8f11c7c8..ef1ba9f61da5 100644
--- a/jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/HttpParser.java
+++ b/jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/HttpParser.java
@@ -167,7 +167,7 @@ public class HttpParser
             for (HttpHeader h : HttpHeader.values())
             {
                 HttpField httpField = new HttpField(h, UNMATCHED_VALUE);
-                map.put(httpField.toString(), httpField);
+                map.put(h + ": ", httpField);
             }
             return map;
         })
diff --git a/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpParserTest.java b/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpParserTest.java
index 57db19b52898..603c314d7684 100644
--- a/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpParserTest.java
+++ b/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpParserTest.java
@@ -358,6 +358,20 @@ public void testLowerCaseVersion(String eoln)
         assertEquals(1, _headers);
     }
 
+    @Test
+    public void testHeaderCache()
+    {
+        assertThat(HttpParser.CACHE.getBest("Content-Type: text/plain\r\n").toString(), is("Content-Type: text/plain"));
+        assertThat(HttpParser.CACHE.getBest("Content-Type: text/plain\n").toString(), is("Content-Type: text/plain"));
+        assertThat(HttpParser.CACHE.getBest("content-type: text/plain\r\n").toString(), is("Content-Type: text/plain"));
+        assertThat(HttpParser.CACHE.getBest("content-type: text/plain\n").toString(), is("Content-Type: text/plain"));
+
+        assertThat(HttpParser.CACHE.getBest("Content-Type: unknown\r\n").toString(), is("Content-Type: \u0000"));
+        assertThat(HttpParser.CACHE.getBest("Content-Type: unknown\n").toString(), is("Content-Type: \u0000"));
+        assertThat(HttpParser.CACHE.getBest("content-type: unknown\r\n").toString(), is("Content-Type: \u0000"));
+        assertThat(HttpParser.CACHE.getBest("content-type: unknown\n").toString(), is("Content-Type: \u0000"));
+    }
+
     @ParameterizedTest
     @ValueSource(strings = {"\r\n", "\n"})
     public void testHeaderCacheNearMiss(String eoln)