diff --git a/RELEASE_NOTES.txt b/RELEASE_NOTES.txt
index 08c2a3900..30cc6af3d 100644
--- a/RELEASE_NOTES.txt
+++ b/RELEASE_NOTES.txt
@@ -11,6 +11,8 @@ Changelog:
 * [HTTPCLIENT-1714] Add HttpClientBuilder.setDnsResolver(DnsResolver).
   Contributed by Alexis Thaveau <alexis.thaveau at gmail.com>
 
+* [HTTPCLIENT-1715] NTLMEngineImpl.Type1Message not thread safe but declared as a constant.
+  Contributed by Olivier Lafontaine <olafontaine at gmail.com>, Gary Gregory <ggregory at apache.org>
 
 
 Release 4.5.1
diff --git a/httpclient/src/main/java/org/apache/http/impl/auth/NTLMEngineImpl.java b/httpclient/src/main/java/org/apache/http/impl/auth/NTLMEngineImpl.java
index 0926e2c09..890f6474c 100644
--- a/httpclient/src/main/java/org/apache/http/impl/auth/NTLMEngineImpl.java
+++ b/httpclient/src/main/java/org/apache/http/impl/auth/NTLMEngineImpl.java
@@ -98,7 +98,7 @@ final class NTLMEngineImpl implements NTLMEngine {
         SIGNATURE[bytesWithoutNull.length] = (byte) 0x00;
     }
 
-    private static final Type1Message TYPE_1_MESSAGE = new Type1Message();
+    private static final String TYPE_1_MESSAGE = new Type1Message().getResponse();
 
     /**
      * Returns the response for the given message.
@@ -145,7 +145,7 @@ final class NTLMEngineImpl implements NTLMEngine {
     static String getType1Message(final String host, final String domain) throws NTLMEngineException {
         // For compatibility reason do not include domain and host in type 1 message
         //return new Type1Message(domain, host).getResponse();
-        return TYPE_1_MESSAGE.getResponse();
+        return TYPE_1_MESSAGE;
     }
 
     /**