diff --git a/retrofit/src/main/java/retrofit2/BuiltInConverters.java b/retrofit/src/main/java/retrofit2/BuiltInConverters.java
index f729383a3153640759cd0bdf046ba9a6cd491e1c..86228d5c37006261030bc99546e4bc30885b8ff0 100644
--- a/retrofit/src/main/java/retrofit2/BuiltInConverters.java
+++ b/retrofit/src/main/java/retrofit2/BuiltInConverters.java
@@ -49,7 +49,7 @@ final class BuiltInConverters extends Converter.Factory {
   static final class VoidResponseBodyConverter implements Converter<ResponseBody, Void> {
     static final VoidResponseBodyConverter INSTANCE = new VoidResponseBodyConverter();
 
-    @Override public Void convert(ResponseBody value) throws IOException {
+    @Override public Void convert(ResponseBody value) {
       value.close();
       return null;
     }
@@ -58,7 +58,7 @@ final class BuiltInConverters extends Converter.Factory {
   static final class RequestBodyConverter implements Converter<RequestBody, RequestBody> {
     static final RequestBodyConverter INSTANCE = new RequestBodyConverter();
 
-    @Override public RequestBody convert(RequestBody value) throws IOException {
+    @Override public RequestBody convert(RequestBody value) {
       return value;
     }
   }
@@ -67,7 +67,7 @@ final class BuiltInConverters extends Converter.Factory {
       implements Converter<ResponseBody, ResponseBody> {
     static final StreamingResponseBodyConverter INSTANCE = new StreamingResponseBodyConverter();
 
-    @Override public ResponseBody convert(ResponseBody value) throws IOException {
+    @Override public ResponseBody convert(ResponseBody value) {
       return value;
     }
   }
diff --git a/retrofit/src/main/java/retrofit2/OkHttpCall.java b/retrofit/src/main/java/retrofit2/OkHttpCall.java
index b4034286e49d6596a828588629e16e4ff08f24df..90e82d7b5b950102ef06dca5c9d4b979892f8e4b 100644
--- a/retrofit/src/main/java/retrofit2/OkHttpCall.java
+++ b/retrofit/src/main/java/retrofit2/OkHttpCall.java
@@ -110,8 +110,7 @@ final class OkHttpCall<T> implements Call<T> {
     }
 
     call.enqueue(new okhttp3.Callback() {
-      @Override public void onResponse(okhttp3.Call call, okhttp3.Response rawResponse)
-          throws IOException {
+      @Override public void onResponse(okhttp3.Call call, okhttp3.Response rawResponse) {
         Response<T> response;
         try {
           response = parseResponse(rawResponse);
@@ -119,7 +118,12 @@ final class OkHttpCall<T> implements Call<T> {
           callFailure(e);
           return;
         }
-        callSuccess(response);
+
+        try {
+          callback.onResponse(OkHttpCall.this, response);
+        } catch (Throwable t) {
+          t.printStackTrace();
+        }
       }
 
       @Override public void onFailure(okhttp3.Call call, IOException e) {
@@ -133,14 +137,6 @@ final class OkHttpCall<T> implements Call<T> {
           t.printStackTrace();
         }
       }
-
-      private void callSuccess(Response<T> response) {
-        try {
-          callback.onResponse(OkHttpCall.this, response);
-        } catch (Throwable t) {
-          t.printStackTrace();
-        }
-      }
     });
   }
 
diff --git a/retrofit/src/main/java/retrofit2/ParameterHandler.java b/retrofit/src/main/java/retrofit2/ParameterHandler.java
index 10238b026fd5c09aba535bf8b2d6712aef570d51..9294134186855440619bb9cb0c2009f6e3b24915 100644
--- a/retrofit/src/main/java/retrofit2/ParameterHandler.java
+++ b/retrofit/src/main/java/retrofit2/ParameterHandler.java
@@ -297,8 +297,7 @@ abstract class ParameterHandler<T> {
     private RawPart() {
     }
 
-    @Override void apply(RequestBuilder builder, @Nullable MultipartBody.Part value)
-        throws IOException {
+    @Override void apply(RequestBuilder builder, @Nullable MultipartBody.Part value) {
       if (value != null) { // Skip null values.
         builder.addPart(value);
       }
diff --git a/retrofit/src/main/java/retrofit2/Utils.java b/retrofit/src/main/java/retrofit2/Utils.java
index 80dd6cb0fbf807b8048f5153d41f9b938402820c..12544e357d47ae5f3da5e681bde34bbd6e133005 100644
--- a/retrofit/src/main/java/retrofit2/Utils.java
+++ b/retrofit/src/main/java/retrofit2/Utils.java
@@ -82,7 +82,9 @@ final class Utils {
       if (!(b instanceof ParameterizedType)) return false;
       ParameterizedType pa = (ParameterizedType) a;
       ParameterizedType pb = (ParameterizedType) b;
-      return equal(pa.getOwnerType(), pb.getOwnerType())
+      Object ownerA = pa.getOwnerType();
+      Object ownerB = pb.getOwnerType();
+      return (ownerA == ownerB || (ownerA != null && ownerA.equals(ownerB)))
           && pa.getRawType().equals(pb.getRawType())
           && Arrays.equals(pa.getActualTypeArguments(), pb.getActualTypeArguments());
 
@@ -155,14 +157,6 @@ final class Utils {
     throw new NoSuchElementException();
   }
 
-  private static boolean equal(Object a, Object b) {
-    return a == b || (a != null && a.equals(b));
-  }
-
-  static int hashCodeOrZero(Object o) {
-    return o != null ? o.hashCode() : 0;
-  }
-
   static String typeToString(Type type) {
     return type instanceof Class ? ((Class<?>) type).getName() : type.toString();
   }
@@ -330,7 +324,7 @@ final class Utils {
     return paramType;
   }
 
-  static boolean hasUnresolvableType(Type type) {
+  static boolean hasUnresolvableType(@Nullable Type type) {
     if (type instanceof Class<?>) {
       return false;
     }
@@ -370,7 +364,7 @@ final class Utils {
     private final Type rawType;
     private final Type[] typeArguments;
 
-    ParameterizedTypeImpl(Type ownerType, Type rawType, Type... typeArguments) {
+    ParameterizedTypeImpl(@Nullable Type ownerType, Type rawType, Type... typeArguments) {
       // Require an owner type if the raw type needs it.
       if (rawType instanceof Class<?>
           && (ownerType == null) != (((Class<?>) rawType).getEnclosingClass() == null)) {
@@ -404,7 +398,9 @@ final class Utils {
     }
 
     @Override public int hashCode() {
-      return Arrays.hashCode(typeArguments) ^ rawType.hashCode() ^ hashCodeOrZero(ownerType);
+      return Arrays.hashCode(typeArguments)
+          ^ rawType.hashCode()
+          ^ (ownerType != null ? ownerType.hashCode() : 0);
     }
 
     @Override public String toString() {