diff --git a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/JsonpTransportHandler.java b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/JsonpTransportHandler.java
index 2bf3a3feba..585fcb2272 100644
--- a/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/JsonpTransportHandler.java
+++ b/spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/JsonpTransportHandler.java
@@ -61,7 +61,8 @@ public class JsonpTransportHandler extends AbstractHttpReceivingTransportHandler
 
 	@Override
 	protected String[] readMessages(ServerHttpRequest request) throws IOException {
-		if (MediaType.APPLICATION_FORM_URLENCODED.equals(request.getHeaders().getContentType())) {
+		MediaType contentType = request.getHeaders().getContentType();
+		if ((contentType != null) && MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(contentType)) {
 			MultiValueMap<String, String> map = this.formConverter.read(null, request);
 			String d = map.getFirst("d");
 			return (StringUtils.hasText(d)) ? getObjectMapper().readValue(d, String[].class) : null;
diff --git a/spring-websocket/src/test/java/org/springframework/web/socket/sockjs/transport/HttpReceivingTransportHandlerTests.java b/spring-websocket/src/test/java/org/springframework/web/socket/sockjs/transport/HttpReceivingTransportHandlerTests.java
index 244c2edb6c..ee184d0fd6 100644
--- a/spring-websocket/src/test/java/org/springframework/web/socket/sockjs/transport/HttpReceivingTransportHandlerTests.java
+++ b/spring-websocket/src/test/java/org/springframework/web/socket/sockjs/transport/HttpReceivingTransportHandlerTests.java
@@ -73,6 +73,18 @@ public class HttpReceivingTransportHandlerTests  extends AbstractHttpRequestTest
 		assertEquals("ok", this.servletResponse.getContentAsString());
 	}
 
+	// SPR-10621
+
+	@Test
+	public void readMessagesJsonpFormEncodedWithEncoding() throws Exception {
+		this.servletRequest.setContent("d=[\"x\"]".getBytes("UTF-8"));
+		this.servletRequest.setContentType("application/x-www-form-urlencoded;charset=UTF-8");
+		handleRequest(new JsonpTransportHandler());
+
+		assertEquals(200, this.servletResponse.getStatus());
+		assertEquals("ok", this.servletResponse.getContentAsString());
+	}
+
 	@Test
 	public void readMessagesBadContent() throws Exception {
 		this.servletRequest.setContent("".getBytes("UTF-8"));