diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockPart.java b/spring-test/src/main/java/org/springframework/mock/web/MockPart.java
index 67dfd43a06..d0d6ea98e8 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockPart.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockPart.java
@@ -49,20 +49,22 @@ public class MockPart implements Part {
 
 	/**
 	 * Constructor for a part with byte[] content only.
+	 * @see #getHeaders()
 	 */
-	public MockPart(String name, byte[] content) {
+	public MockPart(String name, @Nullable byte[] content) {
 		this(name, null, content);
 	}
 
 	/**
-	 * Constructor for a part with a filename.
+	 * Constructor for a part with a filename and streamed content.
+	 * @see #getHeaders()
 	 */
 	public MockPart(String name, @Nullable String filename, InputStream content) throws IOException {
 		this(name, filename, FileCopyUtils.copyToByteArray(content));
 	}
 
 	/**
-	 * Constructor for a part with byte[] content only.
+	 * Constructor for a part with a filename and byte[] content.
 	 * @see #getHeaders()
 	 */
 	private MockPart(String name, @Nullable String filename, @Nullable byte[] content) {
diff --git a/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java b/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java
index 77384e9be5..bc921c2118 100644
--- a/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java
+++ b/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java
@@ -20,6 +20,7 @@ import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Collection;
+import java.util.Collections;
 import javax.servlet.http.Part;
 
 import org.springframework.http.HttpHeaders;
@@ -27,7 +28,6 @@ import org.springframework.http.MediaType;
 import org.springframework.util.Assert;
 import org.springframework.util.FileCopyUtils;
 
-
 /**
  * Mock implementation of {@code javax.servlet.http.Part}.
  *
@@ -47,20 +47,22 @@ public class MockPart implements Part {
 
 	/**
 	 * Constructor for a part with byte[] content only.
+	 * @see #getHeaders()
 	 */
 	public MockPart(String name, byte[] content) {
 		this(name, null, content);
 	}
 
 	/**
-	 * Constructor for a part with a filename.
+	 * Constructor for a part with a filename and streamed content.
+	 * @see #getHeaders()
 	 */
 	public MockPart(String name, String filename, InputStream content) throws IOException {
 		this(name, filename, FileCopyUtils.copyToByteArray(content));
 	}
 
 	/**
-	 * Constructor for a part with byte[] content only.
+	 * Constructor for a part with a filename and byte[] content.
 	 * @see #getHeaders()
 	 */
 	private MockPart(String name, String filename, byte[] content) {
@@ -105,7 +107,8 @@ public class MockPart implements Part {
 
 	@Override
 	public Collection<String> getHeaders(String name) {
-		return this.headers.get(name);
+		Collection<String> headerValues = this.headers.get(name);
+		return (headerValues != null ? headerValues : Collections.emptyList());
 	}
 
 	@Override
diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientResponse.java b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientResponse.java
index 58a1da89c7..6e4654d456 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientResponse.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientResponse.java
@@ -146,6 +146,7 @@ public interface ClientResponse extends Closeable {
 	@Override
 	void close();
 
+
 	/**
 	 * Represents the headers of the HTTP response.
 	 * @see ClientResponse#headers()
@@ -175,6 +176,6 @@ public interface ClientResponse extends Closeable {
 		 * Return the headers as a {@link HttpHeaders} instance.
 		 */
 		HttpHeaders asHttpHeaders();
-
 	}
+
 }
diff --git a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractHttpSockJsSession.java b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractHttpSockJsSession.java
index 88bc04685f..7c19710cb2 100644
--- a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractHttpSockJsSession.java
+++ b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractHttpSockJsSession.java
@@ -295,7 +295,7 @@ public abstract class AbstractHttpSockJsSession extends AbstractSockJsSession {
 		synchronized (this.responseLock) {
 			this.messageCache.add(message);
 			if (logger.isTraceEnabled()) {
-				logger.trace(this.messageCache.size() + " message(s) to flush in session " + this.getId());
+				logger.trace(this.messageCache.size() + " message(s) to flush in session " + getId());
 			}
 			if (isActive() && this.readyToSend) {
 				if (logger.isTraceEnabled()) {