diff --git a/spring-security-kerberos-web/src/main/java/org/springframework/security/kerberos/web/authentication/SpnegoAuthenticationProcessingFilter.java b/spring-security-kerberos-web/src/main/java/org/springframework/security/kerberos/web/authentication/SpnegoAuthenticationProcessingFilter.java
index e3a8456..6739341 100644
--- a/spring-security-kerberos-web/src/main/java/org/springframework/security/kerberos/web/authentication/SpnegoAuthenticationProcessingFilter.java
+++ b/spring-security-kerberos-web/src/main/java/org/springframework/security/kerberos/web/authentication/SpnegoAuthenticationProcessingFilter.java
@@ -115,6 +115,14 @@ public class SpnegoAuthenticationProcessingFilter extends GenericFilterBean {
     private SessionAuthenticationStrategy sessionStrategy = new NullAuthenticatedSessionStrategy();
     private boolean skipIfAlreadyAuthenticated = true;
 
+    /**
+     * Authentication header prefix sent by IE/Windows when the domain controller fails to issue a Kerberos
+     * ticket for the URL.
+     *
+     * "TlRMTVNTUA" is the base64 encoding of "NTLMSSP". This will be followed by the actual token.
+     **/
+    private static final String NTLMSSP_PREFIX = "Negotiate TlRMTVNTUA";
+
     @Override
     public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
         HttpServletRequest request = (HttpServletRequest) req;
@@ -132,7 +140,7 @@ public class SpnegoAuthenticationProcessingFilter extends GenericFilterBean {
 
         String header = request.getHeader("Authorization");
 
-        if (header != null && (header.startsWith("Negotiate ") || header.startsWith("Kerberos "))) {
+        if (header != null && ((header.startsWith("Negotiate ") && !header.startsWith(NTLMSSP_PREFIX)) || header.startsWith("Kerberos "))) {
             if (logger.isDebugEnabled()) {
                 logger.debug("Received Negotiate Header for request " + request.getRequestURL() + ": " + header);
             }
diff --git a/spring-security-kerberos-web/src/test/java/org/springframework/security/kerberos/web/SpnegoAuthenticationProcessingFilterTest.java b/spring-security-kerberos-web/src/test/java/org/springframework/security/kerberos/web/SpnegoAuthenticationProcessingFilterTest.java
index 39c72e6..af85a0e 100644
--- a/spring-security-kerberos-web/src/test/java/org/springframework/security/kerberos/web/SpnegoAuthenticationProcessingFilterTest.java
+++ b/spring-security-kerberos-web/src/test/java/org/springframework/security/kerberos/web/SpnegoAuthenticationProcessingFilterTest.java
@@ -92,6 +92,8 @@ public class SpnegoAuthenticationProcessingFilterTest {
 
     private static final String TOKEN_PREFIX_KERB = "Kerberos ";
 
+    private static final String TOKEN_NTLM = "Negotiate TlRMTVNTUAABAAAAl4II4gAAAAAAAAAAAAAAAAAAAAAGAbEdAAAADw==";
+
 	private static final BadCredentialsException BCE = new BadCredentialsException("");
 
     @Before
@@ -132,7 +134,7 @@ public class SpnegoAuthenticationProcessingFilterTest {
         everythingWorks(tokenPrefix);
 		verify(successHandler).onAuthenticationSuccess(request, response, AUTHENTICATION);
 		verify(failureHandler, never()).onAuthenticationFailure(any(HttpServletRequest.class),
-				any(HttpServletResponse.class), any(AuthenticationException.class));
+                any(HttpServletResponse.class), any(AuthenticationException.class));
     }
 
     private void everythingWorks(String tokenPrefix) throws IOException,
@@ -160,6 +162,19 @@ public class SpnegoAuthenticationProcessingFilterTest {
 		assertEquals(null, SecurityContextHolder.getContext().getAuthentication());
     }
 
+    @Test
+    public void testNTLMSSPHeader() throws Exception {
+        when(request.getHeader(HEADER)).thenReturn(TOKEN_NTLM);
+
+        filter.doFilter(request, response, chain);
+        // If the header is not present, the filter is not allowed to call
+        // authenticate()
+		verify(authenticationManager, never()).authenticate(any(Authentication.class));
+        // chain should go on
+		verify(chain).doFilter(request, response);
+		assertEquals(null, SecurityContextHolder.getContext().getAuthentication());
+    }
+
     @Test
     public void testAuthenticationFails() throws Exception {
         authenticationFails();