diff --git a/.circleci/config.yml b/.circleci/config.yml
index ce5855b..2cb624d 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -16,11 +16,20 @@ workflows:
       - test-linux:
           name: Java 11 - Linux - OpenJDK
           docker-image: cimg/openjdk:11.0
+          requires:
+            - build-linux
+      - test-linux:
+          name: Java 17 - Linux - OpenJDK
+          docker-image: cimg/openjdk:17.0
           with-coverage: true
           requires:
             - build-linux
       - build-test-windows:
           name: Java 11 - Windows - OpenJDK
+          openjdk-version: 11.0.2.01
+      - build-test-windows:
+          name: Java 17 - Windows - OpenJDK
+          openjdk-version: 17.0.1
       - build-test-android:
           name: Android
 
@@ -86,17 +95,20 @@ jobs:
                 path: coverage
 
   build-test-windows:
+    parameters:
+      openjdk-version:
+        type: string
     executor:
       name: win/vs2019
       shell: powershell.exe
     steps:
       - checkout
+      - run:
+          name: uninstall previous openjdk
+          command: choco uninstall openjdk
       - run:
           name: install OpenJDK
-          command: |
-            $ProgressPreference = "SilentlyContinue"  # prevents console errors from CircleCI host
-            iwr -outf openjdk.msi https://developers.redhat.com/download-manager/file/java-11-openjdk-11.0.5.10-2.windows.redhat.x86_64.msi
-            Start-Process msiexec.exe -Wait -ArgumentList '/I openjdk.msi /quiet'
+          command: choco install openjdk --version <<parameters.openjdk-version>>
       - run:
           name: build and test
           command: |
diff --git a/build-android.gradle b/build-android.gradle
index 9c48943..0329994 100644
--- a/build-android.gradle
+++ b/build-android.gradle
@@ -6,7 +6,6 @@ buildscript {
         mavenCentral()
         mavenLocal()
         google()
-        jcenter()
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:4.2.0'
diff --git a/buildSrc/build.gradle.kts b/buildSrc/build.gradle.kts
index a0a9171..8fe36d0 100644
--- a/buildSrc/build.gradle.kts
+++ b/buildSrc/build.gradle.kts
@@ -16,5 +16,5 @@ plugins {
 }
 
 repositories {
-    jcenter()
+    gradlePluginPortal()
 }
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index f3d88b1..e708b1c 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 442d913..2e6e589 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.3.3-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 2fe81a7..4f906e0 100755
--- a/gradlew
+++ b/gradlew
@@ -82,6 +82,7 @@ esac
 
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
+
 # Determine the Java command to use to start the JVM.
 if [ -n "$JAVA_HOME" ] ; then
     if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
@@ -129,6 +130,7 @@ fi
 if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
     APP_HOME=`cygpath --path --mixed "$APP_HOME"`
     CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+
     JAVACMD=`cygpath --unix "$JAVACMD"`
 
     # We build the pattern for arguments to be converted via cygpath
diff --git a/gradlew.bat b/gradlew.bat
index 9109989..ac1b06f 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -40,7 +40,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto init
+if "%ERRORLEVEL%" == "0" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -54,7 +54,7 @@ goto fail
 set JAVA_HOME=%JAVA_HOME:"=%
 set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
-if exist "%JAVA_EXE%" goto init
+if exist "%JAVA_EXE%" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
@@ -64,28 +64,14 @@ echo location of your Java installation.
 
 goto fail
 
-:init
-@rem Get command-line arguments, handling Windows variants
-
-if not "%OS%" == "Windows_NT" goto win9xME_args
-
-:win9xME_args
-@rem Slurp the command line arguments.
-set CMD_LINE_ARGS=
-set _SKIP=2
-
-:win9xME_args_slurp
-if "x%~1" == "x" goto execute
-
-set CMD_LINE_ARGS=%*
-
 :execute
 @rem Setup the command line
 
 set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
+
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
 
 :end
 @rem End local scope for the variables with windows NT shell
diff --git a/src/main/java/com/launchdarkly/sdk/LDValue.java b/src/main/java/com/launchdarkly/sdk/LDValue.java
index 956dc7f..bf36572 100644
--- a/src/main/java/com/launchdarkly/sdk/LDValue.java
+++ b/src/main/java/com/launchdarkly/sdk/LDValue.java
@@ -45,8 +45,6 @@
  */
 @JsonAdapter(LDValueTypeAdapter.class)
 public abstract class LDValue implements JsonSerializable {
-  static final Gson gson = new Gson();
-  
   /**
    * Returns the same value if non-null, or {@link #ofNull()} if null.
    * 
@@ -393,7 +391,7 @@ public LDValue get(String name) {
    * @return a JSON string
    */
   public String toJsonString() {
-    return gson.toJson(this);
+    return JsonSerialization.serialize(this);
   }
   
   abstract void write(JsonWriter writer) throws IOException;
diff --git a/src/main/java/com/launchdarkly/sdk/json/JsonSerialization.java b/src/main/java/com/launchdarkly/sdk/json/JsonSerialization.java
index 8cadeb2..034717c 100644
--- a/src/main/java/com/launchdarkly/sdk/json/JsonSerialization.java
+++ b/src/main/java/com/launchdarkly/sdk/json/JsonSerialization.java
@@ -1,6 +1,7 @@
 package com.launchdarkly.sdk.json;
 
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 import com.launchdarkly.sdk.EvaluationDetail;
 import com.launchdarkly.sdk.EvaluationReason;
 import com.launchdarkly.sdk.LDUser;
@@ -35,7 +36,10 @@ private JsonSerialization() {}
   
   static final List<Class<? extends JsonSerializable>> knownDeserializableClasses = new ArrayList<>();
   
-  private static final Gson gson = new Gson();
+  // This Gson instance has serializeNulls enabled because we want the decision of whether to include
+  // a null property value to be left up to our own serializers. The default behavior would mean that
+  // the GsonWriter would not allow us to write a null property value ever. 
+  private static final Gson gson = new GsonBuilder().serializeNulls().create();
   
   /**
    * Converts an object to its JSON representation.
diff --git a/src/test/java/com/launchdarkly/sdk/json/JsonTestHelpers.java b/src/test/java/com/launchdarkly/sdk/json/JsonTestHelpers.java
index f80546e..667dc54 100644
--- a/src/test/java/com/launchdarkly/sdk/json/JsonTestHelpers.java
+++ b/src/test/java/com/launchdarkly/sdk/json/JsonTestHelpers.java
@@ -15,7 +15,7 @@
 
 @SuppressWarnings("javadoc")
 public abstract class JsonTestHelpers extends BaseTest {
-  static final Gson gson = new Gson();
+  static final Gson gson = new GsonBuilder().serializeNulls().create();
 
   // Note that when we verify the behavior of Gson with LDGson in this project's unit tests, that
   // is not an adequate test for whether the adapters will work in the Java SDK where there is the
@@ -24,7 +24,7 @@ public abstract class JsonTestHelpers extends BaseTest {
   // that the adapters work correctly if Gson actually uses them.
   
   public static Gson configureGson() {
-    return new GsonBuilder().registerTypeAdapterFactory(LDGson.typeAdapters()).create();
+    return new GsonBuilder().serializeNulls().registerTypeAdapterFactory(LDGson.typeAdapters()).create();
   }
   
   public static ObjectMapper configureJacksonMapper() {
diff --git a/src/test/java/com/launchdarkly/sdk/json/LDGsonTest.java b/src/test/java/com/launchdarkly/sdk/json/LDGsonTest.java
index d493d8e..5f03611 100644
--- a/src/test/java/com/launchdarkly/sdk/json/LDGsonTest.java
+++ b/src/test/java/com/launchdarkly/sdk/json/LDGsonTest.java
@@ -63,7 +63,7 @@ public void valueMapToJsonElementMap() {
   public void complexObjectToJsonTree() {
     LDUser user = new LDUser.Builder("userkey").name("name")
         .custom("attr1", LDValue.ofNull())
-        .custom("atrt2", LDValue.of(true))
+        .custom("attr2", LDValue.of(true))
         .custom("attr3", LDValue.of(false))
         .custom("attr4", LDValue.of(0))
         .custom("attr5", LDValue.of(1))
diff --git a/src/test/java/com/launchdarkly/sdk/json/LDValueJsonSerializationTest.java b/src/test/java/com/launchdarkly/sdk/json/LDValueJsonSerializationTest.java
index 04cd551..8e443d7 100644
--- a/src/test/java/com/launchdarkly/sdk/json/LDValueJsonSerializationTest.java
+++ b/src/test/java/com/launchdarkly/sdk/json/LDValueJsonSerializationTest.java
@@ -31,6 +31,7 @@ public void jsonEncodingForNonNullValues() throws Exception {
     verifyValueSerialization(LDValue.of(2.5d), "2.5");
     verifyValueSerialization(JsonTestHelpers.basicArrayValue(), "[2,\"x\"]");
     verifyValueSerialization(JsonTestHelpers.basicObjectValue(), "{\"x\":2}");
+    verifyValueSerialization(LDValue.buildObject().put("x",  LDValue.ofNull()).build(), "{\"x\":null}");
     verifyDeserializeInvalidJson(LDValue.class, "]");
   }