diff --git a/build.gradle b/build.gradle
index 336aeffbbe6..7bf0a4b727f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,7 +1,8 @@
 buildscript {
-	ext.kotlinVersion = '1.1.3-2'
+	ext.kotlinVersion = '1.1.4-eap-33'
 	repositories {
 		maven { url "https://repo.spring.io/plugins-release" }
+		maven { url "https://dl.bintray.com/kotlin/kotlin-eap-1.1" }
 	}
 	dependencies {
 		classpath("io.spring.gradle:dependency-management-plugin:1.0.0.RELEASE")
@@ -112,12 +113,12 @@ configure(allprojects) { project ->
 	apply plugin: "kotlin"
 	compileKotlin {
 		kotlinOptions.jvmTarget = "1.8"
-		kotlinOptions.freeCompilerArgs = ["-Xskip-runtime-version-check"]
+		kotlinOptions.freeCompilerArgs = ["-Xskip-runtime-version-check", "-Xload-jsr305-annotations"]
 
 	}
 	compileTestKotlin {
 		kotlinOptions.jvmTarget = "1.8"
-		kotlinOptions.freeCompilerArgs = ["-Xskip-runtime-version-check"]
+		kotlinOptions.freeCompilerArgs = ["-Xskip-runtime-version-check", "-Xload-jsr305-annotations"]
 	}
 
 	configurations.all {
@@ -176,6 +177,7 @@ configure(allprojects) { project ->
 		maven { url "https://repo.spring.io/libs-release" }
 		maven { url "https://repo.spring.io/milestone" }
 		maven { url "https://repo.spring.io/snapshot" }
+		maven { url "https://dl.bintray.com/kotlin/kotlin-eap-1.1" }
 	}
 
 	dependencies {
diff --git a/spring-beans/src/test/kotlin/org/springframework/beans/BeanUtilsKotlinTests.kt b/spring-beans/src/test/kotlin/org/springframework/beans/BeanUtilsKotlinTests.kt
index c7c4040e248..bdcdcf95fa6 100644
--- a/spring-beans/src/test/kotlin/org/springframework/beans/BeanUtilsKotlinTests.kt
+++ b/spring-beans/src/test/kotlin/org/springframework/beans/BeanUtilsKotlinTests.kt
@@ -28,32 +28,32 @@ class BeanUtilsKotlinTests {
 
 	@Test
 	fun `Instantiate immutable class`() {
-		val constructor = BeanUtils.findPrimaryConstructor(Foo::class.java)
-		val foo = BeanUtils.instantiateClass(constructor, "bar", 3) as Foo
+		val constructor = BeanUtils.findPrimaryConstructor(Foo::class.java)!!
+		val foo = BeanUtils.instantiateClass(constructor, "bar", 3)
 		assertEquals("bar", foo.param1)
 		assertEquals(3, foo.param2)
 	}
 
 	@Test
 	fun `Instantiate immutable class with optional parameter and all parameters specified`() {
-		val constructor = BeanUtils.findPrimaryConstructor(Bar::class.java)
-		val bar = BeanUtils.instantiateClass(constructor, "baz", 8) as Bar
+		val constructor = BeanUtils.findPrimaryConstructor(Bar::class.java)!!
+		val bar = BeanUtils.instantiateClass(constructor, "baz", 8)
 		assertEquals("baz", bar.param1)
 		assertEquals(8, bar.param2)
 	}
 
 	@Test
 	fun `Instantiate immutable class with optional parameter and only mandatory parameters specified by position`() {
-		val constructor = BeanUtils.findPrimaryConstructor(Bar::class.java)
-		val bar = BeanUtils.instantiateClass(constructor, "baz") as Bar
+		val constructor = BeanUtils.findPrimaryConstructor(Bar::class.java)!!
+		val bar = BeanUtils.instantiateClass(constructor, "baz")
 		assertEquals("baz", bar.param1)
 		assertEquals(12, bar.param2)
 	}
 
 	@Test
 	fun `Instantiate immutable class with optional parameter specified with null value`() {
-		val constructor = BeanUtils.findPrimaryConstructor(Bar::class.java)
-		val bar = BeanUtils.instantiateClass(constructor, "baz", null) as Bar
+		val constructor = BeanUtils.findPrimaryConstructor(Bar::class.java)!!
+		val bar = BeanUtils.instantiateClass(constructor, "baz", null)
 		assertEquals("baz", bar.param1)
 		assertEquals(12, bar.param2)
 	}
diff --git a/spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessageHeaderAccessor.java b/spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessageHeaderAccessor.java
index e08a83fd89c..ad63adeee45 100644
--- a/spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessageHeaderAccessor.java
+++ b/spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessageHeaderAccessor.java
@@ -130,7 +130,7 @@ public class SimpMessageHeaderAccessor extends NativeMessageHeaderAccessor {
 		return (String) getHeader(DESTINATION_HEADER);
 	}
 
-	public void setSubscriptionId(String subscriptionId) {
+	public void setSubscriptionId(@Nullable String subscriptionId) {
 		setHeader(SUBSCRIPTION_ID_HEADER, subscriptionId);
 	}
 
@@ -139,7 +139,7 @@ public class SimpMessageHeaderAccessor extends NativeMessageHeaderAccessor {
 		return (String) getHeader(SUBSCRIPTION_ID_HEADER);
 	}
 
-	public void setSessionId(String sessionId) {
+	public void setSessionId(@Nullable String sessionId) {
 		setHeader(SESSION_ID_HEADER, sessionId);
 	}
 
diff --git a/spring-messaging/src/test/kotlin/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandlerKotlinTests.kt b/spring-messaging/src/test/kotlin/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandlerKotlinTests.kt
index ea43eae237c..50f7a2734f2 100644
--- a/spring-messaging/src/test/kotlin/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandlerKotlinTests.kt
+++ b/spring-messaging/src/test/kotlin/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandlerKotlinTests.kt
@@ -155,7 +155,7 @@ class SimpAnnotationMethodMessageHandlerKotlinTests {
                                                          clientOutboundChannel: MessageChannel) :
             SimpAnnotationMethodMessageHandler(clientInboundChannel, clientOutboundChannel, brokerTemplate) {
 
-        fun registerHandler(handler: Any?) {
+        fun registerHandler(handler: Any) {
             super.detectHandlerMethods(handler)
         }
     }
diff --git a/spring-web/src/test/kotlin/org/springframework/web/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt b/spring-web/src/test/kotlin/org/springframework/web/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt
index aac0ba426fa..1f587cb145e 100644
--- a/spring-web/src/test/kotlin/org/springframework/web/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt
+++ b/spring-web/src/test/kotlin/org/springframework/web/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt
@@ -76,7 +76,7 @@ class RequestParamMethodArgumentResolverKotlinTests {
 		val method = ReflectionUtils.findMethod(javaClass, "handle", String::class.java,
 				String::class.java, String::class.java, String::class.java,
 				MultipartFile::class.java, MultipartFile::class.java,
-				MultipartFile::class.java, MultipartFile::class.java)
+				MultipartFile::class.java, MultipartFile::class.java)!!
 
 		nullableParamRequired = SynthesizingMethodParameter(method, 0)
 		nullableParamNotRequired = SynthesizingMethodParameter(method, 1)
diff --git a/spring-webflux/src/test/kotlin/org/springframework/web/reactive/result/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt b/spring-webflux/src/test/kotlin/org/springframework/web/reactive/result/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt
index 940055e37a3..11a3d6ff863 100644
--- a/spring-webflux/src/test/kotlin/org/springframework/web/reactive/result/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt
+++ b/spring-webflux/src/test/kotlin/org/springframework/web/reactive/result/method/annotation/RequestParamMethodArgumentResolverKotlinTests.kt
@@ -54,7 +54,7 @@ class RequestParamMethodArgumentResolverKotlinTests {
 		bindingContext = BindingContext(initializer)
 
 		val method = ReflectionUtils.findMethod(javaClass, "handle", String::class.java,
-				String::class.java, String::class.java, String::class.java)
+				String::class.java, String::class.java, String::class.java)!!
 
 		nullableParamRequired = SynthesizingMethodParameter(method, 0)
 		nullableParamNotRequired = SynthesizingMethodParameter(method, 1)