diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataRequest.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataRequest.java
index 5b734ecb8..4f364e186 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataRequest.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataRequest.java
@@ -60,6 +60,30 @@ public class ODataRequest {
     this.method = method;
   }
 
+  /**
+   * <p>Set a header to the response.</p>
+   * <p>The header name will be handled as case-insensitive key.</p>
+   * <p>If a header already exists then the header will be replaced by this new value.</p>
+   * @param name case-insensitive header name
+   * @param value value for the given header name
+   * @see <a href="http://ietf.org/rfc/rfc7230.txt">RFC 7230, section 3.2.2</a>
+   */
+  public void setHeader(final String name, final String value) {
+    headers.setHeader(name, value);
+  }
+
+  /**
+   * <p>Adds a header to the request.</p>
+   * <p>The header name will be handled as case-insensitive key.</p>
+   * <p>If a header already exists then the list of values will just be extended.</p>
+   * @param name case-insensitive header name
+   * @param value value for the given header name
+   * @see <a href="http://ietf.org/rfc/rfc7230.txt">RFC 7230, section 3.2.2</a>
+   */
+  public void addHeader(final String name, final String value) {
+    headers.addHeader(name, value);
+  }
+
   /**
    * <p>Adds a header to the request.</p>
    * <p>The header name will be handled as case-insensitive key.</p>
@@ -73,20 +97,20 @@ public class ODataRequest {
   }
 
   /**
-   * Gets header value for a given name.
+   * Get header values for a given name.
    * @param name the header name as a case-insensitive key
    * @return the header value(s) or null if not found
    */
   public List<String> getHeaders(final String name) {
     HttpHeader h = headers.getHeader(name);
     if(h == null) {
-      return null;//Collections.emptyList();
+      return null;
     }
     return new ArrayList<String>(h.getValues());
   }
 
   /**
-   * Gets first header value for a given name.
+   * Get first header value for a given name.
    * @param name the header name as a case-insensitive key
    * @return the first header value or null if not found
    */
diff --git a/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataResponse.java b/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataResponse.java
index b104ff7ca..367ce1696 100644
--- a/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataResponse.java
+++ b/lib/server-api/src/main/java/org/apache/olingo/server/api/ODataResponse.java
@@ -19,9 +19,11 @@
 package org.apache.olingo.server.api;
 
 import java.io.InputStream;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import org.apache.olingo.commons.api.http.HttpHeader;
@@ -54,27 +56,81 @@ public class ODataResponse {
   }
 
   /**
-   * Sets a header.
-   * @param name the name
-   * @param value the value
+   * <p>Set a header to the response.</p>
+   * <p>The header name will be handled as case-insensitive key.</p>
+   * <p>If a header already exists then the header will be replaced by this new value.</p>
+   * @param name case-insensitive header name
+   * @param value value for the given header name
+   * @see <a href="http://ietf.org/rfc/rfc7230.txt">RFC 7230, section 3.2.2</a>
    */
   public void setHeader(final String name, final String value) {
     headers.setHeader(name, value);
   }
 
   /**
-   * Gets all headers.
+   * <p>Adds a header to the response.</p>
+   * <p>The header name will be handled as case-insensitive key.</p>
+   * <p>If a header already exists then the list of values will just be extended.</p>
+   * @param name case-insensitive header name
+   * @param value value for the given header name
+   * @see <a href="http://ietf.org/rfc/rfc7230.txt">RFC 7230, section 3.2.2</a>
+   */
+  public void addHeader(final String name, final String value) {
+    headers.setHeader(name, value);
+  }
+
+  /**
+   * <p>Adds a header to the response.</p>
+   * <p>The header name will be handled as case-insensitive key.</p>
+   * <p>If a header already exists then the list of values will just be extended.</p>
+   * @param name case-insensitive header name
+   * @param values list of values for the given header name
+   * @see <a href="http://ietf.org/rfc/rfc7230.txt">RFC 7230, section 3.2.2</a>
+   */
+  public void addHeader(final String name, final List<String> values) {
+    headers.addHeader(name, values);
+  }
+
+  /**
+   * Get all headers with the according values.
+   *
    * @return an unmodifiable Map of header names/values
    */
-  public Map<String, String> getHeaders() {
-    Map<String, String> result = new HashMap<String, String>();
+  public Map<String, List<String>> getAllHeaders() {
+    Map<String, List<String>> result = new HashMap<String, List<String>>();
     Collection<HttpHeader> allHeaders = headers.getHeaders();
     for (HttpHeader header : allHeaders) {
-      result.put(header.getName(), header.getValues().iterator().next());
+      result.put(header.getName(), new ArrayList<String>(header.getValues()));
     }
     return Collections.unmodifiableMap(result);
   }
 
+  /**
+   * Gets header value for a given name.
+   * @param name the header name as a case-insensitive key
+   * @return the header value(s) or null if not found
+   */
+  public List<String> getHeaders(final String name) {
+    HttpHeader h = headers.getHeader(name);
+    if(h == null) {
+      return null;
+    }
+    return new ArrayList<String>(h.getValues());
+  }
+
+  /**
+   * Gets first header value for a given name.
+   * If header name is not known <code>null</code> is returned.
+   *
+   * @param name the header name as a case-insensitive key
+   * @return the first header value or null if not found
+   */
+  public String getHeader(final String name) {
+    final List<String> values = getHeaders(name);
+    return values == null ? null : values.get(0);
+  }
+
+
   /**
    * Sets the content (body).
    * @param content the content as {@link InputStream}
diff --git a/lib/server-core-ext/src/main/java/org/apache/olingo/server/core/responses/ServiceResponse.java b/lib/server-core-ext/src/main/java/org/apache/olingo/server/core/responses/ServiceResponse.java
index deb120630..56ae9f428 100644
--- a/lib/server-core-ext/src/main/java/org/apache/olingo/server/core/responses/ServiceResponse.java
+++ b/lib/server-core-ext/src/main/java/org/apache/olingo/server/core/responses/ServiceResponse.java
@@ -55,7 +55,7 @@ public abstract class ServiceResponse {
     if (!this.closed) {
       if (this.strictApplyPreferences) {
         if (!preferences.isEmpty()) {
-          assert(this.response.getHeaders().get("Preference-Applied") != null);
+          assert(this.response.getAllHeaders().get("Preference-Applied") != null);
         }
       }
       this.closed = true;
@@ -97,7 +97,7 @@ public abstract class ServiceResponse {
 
   public void writeHeader(String key, String value) {
     if ("Preference-Applied".equals(key)) {
-      String previous = this.response.getHeaders().get(key);
+      String previous = this.response.getHeader(key);
       if (previous != null) {
         value = previous+";"+value;
       }
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHandler.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHandler.java
index bfbc5ac3d..80d548a86 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHandler.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHandler.java
@@ -117,7 +117,9 @@ public class ODataHandler {
 
   private void processInternal(final ODataRequest request, final ODataResponse response)
       throws ODataApplicationException, ODataLibraryException {
-    validateODataVersion(request, response);
+    response.setHeader(HttpHeader.ODATA_VERSION, ODataServiceVersion.V40.toString());
+
+    validateODataVersion(request);
 
     int measurementUriParser = debugger.startRuntimeMeasurement("UriParser", "parseUri");
     uriInfo = new Parser().parseUri(request.getRawODataPath(), request.getRawQueryPath(), null,
@@ -157,11 +159,9 @@ public class ODataHandler {
     debugger.stopRuntimeMeasurement(measurementHandle);
   }
 
-  private void validateODataVersion(final ODataRequest request, final ODataResponse response)
+  private void validateODataVersion(final ODataRequest request)
       throws ODataHandlerException {
     final String maxVersion = request.getHeader(HttpHeader.ODATA_MAX_VERSION);
-    response.setHeader(HttpHeader.ODATA_VERSION, ODataServiceVersion.V40.toString());
-
     if (maxVersion != null) {
       if (ODataServiceVersion.isBiggerThan(ODataServiceVersion.V40.toString(), maxVersion)) {
         throw new ODataHandlerException("ODataVersion not supported: " + maxVersion,
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHttpHandlerImpl.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHttpHandlerImpl.java
index e4435917b..fbcc230b8 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHttpHandlerImpl.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/ODataHttpHandlerImpl.java
@@ -147,8 +147,10 @@ public class ODataHttpHandlerImpl implements ODataHttpHandler {
   static void convertToHttp(final HttpServletResponse response, final ODataResponse odResponse) {
     response.setStatus(odResponse.getStatusCode());
 
-    for (Entry<String, String> entry : odResponse.getHeaders().entrySet()) {
-      response.setHeader(entry.getKey(), entry.getValue());
+    for (Entry<String, List<String>> entry : odResponse.getAllHeaders().entrySet()) {
+      for (String headerValue : entry.getValue()) {
+        response.addHeader(entry.getKey(), headerValue);
+      }
     }
 
     InputStream input = odResponse.getContent();
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/batchhandler/referenceRewriting/BatchReferenceRewriter.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/batchhandler/referenceRewriting/BatchReferenceRewriter.java
index 31d201040..a941c336d 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/batchhandler/referenceRewriting/BatchReferenceRewriter.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/batchhandler/referenceRewriting/BatchReferenceRewriter.java
@@ -78,7 +78,7 @@ public class BatchReferenceRewriter {
     if (request.getMethod() == HttpMethod.POST) {
       // Create entity
       // The URI of the new resource will be generated by the server and published in the location header
-      final String locationHeader = response.getHeaders().get(HttpHeader.LOCATION);
+      final String locationHeader = response.getHeader(HttpHeader.LOCATION);
       resourceUri = locationHeader == null ? null : parseODataPath(locationHeader, request.getRawBaseUri());
     } else {
       // Update, Upsert (PUT, PATCH, Delete)
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugResponseHelperImpl.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugResponseHelperImpl.java
index fa07f94c7..3a1c2e0dc 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugResponseHelperImpl.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugResponseHelperImpl.java
@@ -73,7 +73,7 @@ public class DebugResponseHelperImpl implements DebugResponseHelper {
       switch (requestedFormat) {
       case DOWNLOAD:
         response.setHeader("Content-Disposition", "attachment; filename=OData-Response."
-            + new Date().toString().replace(' ', '_').replace(':', '.') + ".html");
+                + new Date().toString().replace(' ', '_').replace(':', '.') + ".html");
         // Download is the same as html except for the above header
       case HTML:
         String title = debugInfo.getRequest() == null ?
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabBody.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabBody.java
index 5608d584a..e0330b81e 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabBody.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabBody.java
@@ -52,7 +52,7 @@ public class DebugTabBody implements DebugTab {
     this.response = response;
     this.serviceRoot = serviceRoot == null ? "/" : serviceRoot;
     if (response != null) {
-      final String contentType = response.getHeaders().get(HttpHeader.CONTENT_TYPE);
+      final String contentType = response.getHeader(HttpHeader.CONTENT_TYPE);
       // TODO: Differentiate better
       if (contentType != null) {
         responseContent = ResponseContent.JSON;
@@ -125,7 +125,7 @@ public class DebugTabBody implements DebugTab {
       break;
     case IMAGE:
       // Make header query case insensitive
-      writer.append("<img src=\"data:").append(response.getHeaders().get(HttpHeader.CONTENT_TYPE)).append(";base64,")
+      writer.append("<img src=\"data:").append(response.getHeader(HttpHeader.CONTENT_TYPE)).append(";base64,")
           .append(body)
           .append("\" />\n");
       break;
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabResponse.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabResponse.java
index 528cf6160..11331a9ce 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabResponse.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/debug/DebugTabResponse.java
@@ -21,6 +21,8 @@ package org.apache.olingo.server.core.debug;
 import java.io.IOException;
 import java.io.Writer;
 import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import org.apache.olingo.commons.api.http.HttpStatusCode;
@@ -36,13 +38,13 @@ public class DebugTabResponse implements DebugTab {
   private final ODataResponse response;
   private final String serviceRoot;
   private final HttpStatusCode status;
-  private final Map<String, String> headers;
+  private final Map<String, List<String>> headers;
 
   public DebugTabResponse(final ODataResponse applicationResponse, final String serviceRoot) {
     this.response = applicationResponse;
     if (response != null) {
       status = HttpStatusCode.fromStatusCode(response.getStatusCode());
-      headers = response.getHeaders();
+      headers = response.getAllHeaders();
     } else {
       status = HttpStatusCode.INTERNAL_SERVER_ERROR;
       headers = Collections.emptyMap();
@@ -69,7 +71,7 @@ public class DebugTabResponse implements DebugTab {
 
     if (headers != null && !headers.isEmpty()) {
       gen.writeFieldName("headers");
-      DebugResponseHelperImpl.appendJsonTable(gen, headers);
+      DebugResponseHelperImpl.appendJsonTable(gen, map(headers));
     }
 
     gen.writeFieldName("body");
@@ -82,13 +84,25 @@ public class DebugTabResponse implements DebugTab {
     gen.writeEndObject();
   }
 
+  private Map<String, String> map(Map<String, List<String>> headers) {
+    Map<String, String> result = new HashMap<String, String>();
+    for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
+      if(entry.getValue().size() == 1) {
+        result.put(entry.getKey(), entry.getValue().get(0));
+      } else {
+        result.put(entry.getKey(), entry.getValue().toString());
+      }
+    }
+    return result;
+  }
+
   @Override
   public void appendHtml(final Writer writer) throws IOException {
     writer.append("<h2>Status Code</h2>\n")
         .append("<p>").append(Integer.toString(status.getStatusCode())).append(' ')
         .append(status.getInfo()).append("</p>\n")
         .append("<h2>Response Headers</h2>\n");
-    DebugResponseHelperImpl.appendHtmlTable(writer, headers);
+    DebugResponseHelperImpl.appendHtmlTable(writer, map(headers));
     writer.append("<h2>Response Body</h2>\n");
     if (response != null && response.getContent() != null) {
       new DebugTabBody(response, serviceRoot).appendHtml(writer);
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/AsyncResponseSerializer.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/AsyncResponseSerializer.java
index 9c3060e5d..6f431d4af 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/AsyncResponseSerializer.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/AsyncResponseSerializer.java
@@ -31,6 +31,7 @@ import java.nio.ByteBuffer;
 import java.nio.channels.Channels;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.channels.WritableByteChannel;
+import java.util.List;
 import java.util.Map;
 
 public class AsyncResponseSerializer {
@@ -59,16 +60,18 @@ public class AsyncResponseSerializer {
 
   private void appendResponseHeader(final ODataResponse response,
                                     final ByteArrayOutputStream buffer) throws IOException {
-    final Map<String, String> header = response.getHeaders();
+    final Map<String, List<String>> header = response.getAllHeaders();
 
-    for (final Map.Entry<String, String> entry: header.entrySet()) {
+    for (final Map.Entry<String, List<String>> entry: header.entrySet()) {
       appendHeader(entry.getKey(), entry.getValue(), buffer);
     }
   }
 
-  private void appendHeader(final String name, final String value, final ByteArrayOutputStream buffer)
+  private void appendHeader(final String name, final List<String> values, final ByteArrayOutputStream buffer)
       throws IOException {
-    append(name + COLON + SP + value + CRLF, buffer);
+    for (String value : values) {
+      append(name + COLON + SP + value + CRLF, buffer);
+    }
   }
 
   private void appendStatusLine(final ODataResponse response, final ByteArrayOutputStream buffer)
diff --git a/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/BatchResponseSerializer.java b/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/BatchResponseSerializer.java
index d54f0280c..4af94f98b 100644
--- a/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/BatchResponseSerializer.java
+++ b/lib/server-core/src/main/java/org/apache/olingo/server/core/serializer/BatchResponseSerializer.java
@@ -135,12 +135,12 @@ public class BatchResponseSerializer {
 
   private void appendResponseHeader(final ODataResponse response, final int contentLength,
       final BodyBuilder builder) {
-    final Map<String, String> header = response.getHeaders();
+    final Map<String, List<String>> header = response.getAllHeaders();
 
-    for (final Map.Entry<String, String> entry : header.entrySet()) {
+    for (final Map.Entry<String, List<String>> entry : header.entrySet()) {
       // Requests do never has a content id header
       if (!entry.getKey().equalsIgnoreCase(HttpHeader.CONTENT_ID)) {
-        appendHeader(entry.getKey(), entry.getValue(), builder);
+        appendHeader(entry.getKey(), entry.getValue().get(0), builder);
       }
     }
 
@@ -153,8 +153,8 @@ public class BatchResponseSerializer {
     appendHeader(BatchParserCommon.CONTENT_TRANSFER_ENCODING, BatchParserCommon.BINARY_ENCODING, builder);
 
     if (isChangeSet) {
-      if (response.getHeaders().get(HttpHeader.CONTENT_ID) != null) {
-        appendHeader(HttpHeader.CONTENT_ID, response.getHeaders().get(HttpHeader.CONTENT_ID), builder);
+      if (response.getAllHeaders().get(HttpHeader.CONTENT_ID) != null) {
+        appendHeader(HttpHeader.CONTENT_ID, response.getHeader(HttpHeader.CONTENT_ID), builder);
       } else {
         throw new BatchSerializerException("Missing content id", MessageKeys.MISSING_CONTENT_ID);
       }
diff --git a/lib/server-tecsvc/src/main/java/org/apache/olingo/server/tecsvc/async/AsyncProcessor.java b/lib/server-tecsvc/src/main/java/org/apache/olingo/server/tecsvc/async/AsyncProcessor.java
index 9f36e11b9..da16f9b63 100644
--- a/lib/server-tecsvc/src/main/java/org/apache/olingo/server/tecsvc/async/AsyncProcessor.java
+++ b/lib/server-tecsvc/src/main/java/org/apache/olingo/server/tecsvc/async/AsyncProcessor.java
@@ -193,8 +193,8 @@ public class AsyncProcessor<T extends Processor> {
 
   private static ODataResponse createODataResponse(ODataResponse response) {
     ODataResponse created = new ODataResponse();
-    for (Map.Entry<String, String> header : response.getHeaders().entrySet()) {
-      created.setHeader(header.getKey(), header.getValue());
+    for (Map.Entry<String, List<String>> header : response.getAllHeaders().entrySet()) {
+      created.addHeader(header.getKey(), header.getValue());
     }
     return created;
   }
diff --git a/lib/server-test/src/test/java/org/apache/olingo/server/core/ODataHandlerTest.java b/lib/server-test/src/test/java/org/apache/olingo/server/core/ODataHandlerTest.java
index 5b347d15a..8cd470655 100644
--- a/lib/server-test/src/test/java/org/apache/olingo/server/core/ODataHandlerTest.java
+++ b/lib/server-test/src/test/java/org/apache/olingo/server/core/ODataHandlerTest.java
@@ -106,7 +106,7 @@ public class ODataHandlerTest {
     final ODataResponse response = dispatch(HttpMethod.GET, "/", null);
     assertEquals(HttpStatusCode.OK.getStatusCode(), response.getStatusCode());
 
-    String ct = response.getHeaders().get(HttpHeader.CONTENT_TYPE);
+    String ct = response.getHeader(HttpHeader.CONTENT_TYPE);
     assertThat(ct, containsString("application/json"));
     assertThat(ct, containsString("odata.metadata=minimal"));
 
@@ -121,7 +121,7 @@ public class ODataHandlerTest {
   public void serviceDocumentRedirect() throws Exception {
     final ODataResponse response = dispatch(HttpMethod.GET, "", null);
     assertEquals(HttpStatusCode.TEMPORARY_REDIRECT.getStatusCode(), response.getStatusCode());
-    assertEquals(BASE_URI + "/", response.getHeaders().get(HttpHeader.LOCATION));
+    assertEquals(BASE_URI + "/", response.getHeader(HttpHeader.LOCATION));
   }
 
   @Test
@@ -143,7 +143,7 @@ public class ODataHandlerTest {
   public void metadataDefault() throws Exception {
     final ODataResponse response = dispatch(HttpMethod.GET, "$metadata", null);
     assertEquals(HttpStatusCode.OK.getStatusCode(), response.getStatusCode());
-    assertEquals(HttpContentType.APPLICATION_XML, response.getHeaders().get(HttpHeader.CONTENT_TYPE));
+    assertEquals(HttpContentType.APPLICATION_XML, response.getHeader(HttpHeader.CONTENT_TYPE));
 
     assertNotNull(response.getContent());
     assertThat(IOUtils.toString(response.getContent()),
@@ -153,14 +153,14 @@ public class ODataHandlerTest {
   @Test
   public void maxVersionNone() {
     final ODataResponse response = dispatch(HttpMethod.GET, "$metadata", null);
-    assertEquals(ODataServiceVersion.V40.toString(), response.getHeaders().get(HttpHeader.ODATA_VERSION));
+    assertEquals(ODataServiceVersion.V40.toString(), response.getHeader(HttpHeader.ODATA_VERSION));
   }
 
   @Test
   public void maxVersionSupported() {
     final ODataResponse response = dispatch(HttpMethod.GET, "$metadata", null,
         HttpHeader.ODATA_MAX_VERSION, ODataServiceVersion.V40.toString(), null);
-    assertEquals(ODataServiceVersion.V40.toString(), response.getHeaders().get(HttpHeader.ODATA_VERSION));
+    assertEquals(ODataServiceVersion.V40.toString(), response.getHeader(HttpHeader.ODATA_VERSION));
   }
 
   @Test
@@ -168,7 +168,7 @@ public class ODataHandlerTest {
     final ODataResponse response = dispatch(HttpMethod.GET, "$metadata", null,
         HttpHeader.ODATA_MAX_VERSION, ODataServiceVersion.V30.toString(), null);
 
-    assertEquals(ODataServiceVersion.V40.toString(), response.getHeaders().get(HttpHeader.ODATA_VERSION));
+    assertEquals(ODataServiceVersion.V40.toString(), response.getHeader(HttpHeader.ODATA_VERSION));
     assertEquals(HttpStatusCode.BAD_REQUEST.getStatusCode(), response.getStatusCode());
   }