diff --git a/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache b/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
index 4f79dddb9c6..9926c95ae1f 100644
--- a/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
+++ b/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache
@@ -73,6 +73,12 @@ public class ApiClient {
      */
     public ApiClient() {
         httpClient = new OkHttpClient();
+
+        {{#useGzipFeature}}
+        // Enable gzip request compression
+        httpClient.interceptors().add(new GzipRequestInterceptor());
+        {{/useGzipFeature}}
+
         verifyingSsl = true;
         json = new JSON();
 
@@ -835,6 +841,13 @@ public class ApiClient {
             if (returnType == null || response.code() == 204) {
                 // returning null if the returnType is not defined,
                 // or the status code is 204 (No Content)
+                if (response.body() != null) {
+                    try {
+                        response.body().close();
+                    } catch (IOException e) {
+                        throw new ApiException(response.message(), e, response.code(), response.headers().toMultimap());
+                    }
+                }
                 return null;
             } else {
                 return deserialize(response, returnType);
diff --git a/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/JSON.mustache b/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/JSON.mustache
index f306525f6f4..5ee0a44b58b 100644
--- a/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/JSON.mustache
+++ b/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/JSON.mustache
@@ -132,7 +132,8 @@ public class JSON {
      */
     public static class DateTimeTypeAdapter extends TypeAdapter<DateTime> {
 
-        private DateTimeFormatter formatter;
+        private final DateTimeFormatter parseFormatter = ISODateTimeFormat.dateOptionalTimeParser();
+        private final DateTimeFormatter printFormatter = ISODateTimeFormat.dateTime();
 
         public DateTimeTypeAdapter() {
             this(ISODateTimeFormat.dateTime().withOffsetParsed());
@@ -151,7 +152,7 @@ public class JSON {
             if (date == null) {
                 out.nullValue();
             } else {
-                out.value(formatter.print(date));
+                out.value(printFormatter.print(date));
             }
         }
 
@@ -163,7 +164,7 @@ public class JSON {
                     return null;
                 default:
                     String date = in.nextString();
-                    return formatter.parseDateTime(date);
+                    return parseFormatter.parseDateTime(date);
             }
         }
     }
diff --git a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/ApiClient.java b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/ApiClient.java
index c960ab9195d..8410522b276 100644
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/ApiClient.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/io/swagger/client/ApiClient.java
@@ -72,6 +72,8 @@ public class ApiClient {
      */
     public ApiClient() {
         httpClient = new OkHttpClient();
+
+
         verifyingSsl = true;
         json = new JSON();
 
@@ -820,6 +822,13 @@ public class ApiClient {
             if (returnType == null || response.code() == 204) {
                 // returning null if the returnType is not defined,
                 // or the status code is 204 (No Content)
+                if (response.body() != null) {
+                    try {
+                        response.body().close();
+                    } catch (IOException e) {
+                        throw new ApiException(response.message(), e, response.code(), response.headers().toMultimap());
+                    }
+                }
                 return null;
             } else {
                 return deserialize(response, returnType);