diff --git a/baseline.xml b/baseline.xml
new file mode 100644
index 00000000..b5f0a5f9
--- /dev/null
+++ b/baseline.xml
@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<files psalm-version="4.30.0@d0bc6e25d89f649e4f36a534f330f8bb4643dd69">
+  <file src="src/LaunchDarkly/LDClient.php">
+    <DeprecatedClass occurrences="7">
+      <code>LDContext|LDUser</code>
+      <code>LDContext|LDUser</code>
+      <code>LDContext|LDUser</code>
+      <code>LDContext|LDUser</code>
+      <code>LDContext|LDUser</code>
+      <code>LDContext|LDUser</code>
+      <code>LDContext|LDUser</code>
+    </DeprecatedClass>
+  </file>
+  <file src="src/LaunchDarkly/LDContext.php">
+    <DeprecatedClass occurrences="1">
+      <code>LDUser</code>
+    </DeprecatedClass>
+  </file>
+  <file src="src/LaunchDarkly/LDUserBuilder.php">
+    <DeprecatedClass occurrences="3">
+      <code>LDUser</code>
+      <code>LDUser</code>
+    </DeprecatedClass>
+  </file>
+</files>
diff --git a/phpunit.xml b/phpunit.xml
index 10e08aaf..fc621927 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd" bootstrap="vendor/autoload.php" colors="true" beStrictAboutChangesToGlobalState="true" beStrictAboutOutputDuringTests="true" beStrictAboutResourceUsageDuringSmallTests="true" beStrictAboutTestsThatDoNotTestAnything="true" beStrictAboutTodoAnnotatedTests="true" verbose="true" defaultTimeLimit="10">
-  
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd" bootstrap="tests/bootstrap.php" colors="true" beStrictAboutChangesToGlobalState="true" beStrictAboutOutputDuringTests="true" beStrictAboutResourceUsageDuringSmallTests="true" beStrictAboutTestsThatDoNotTestAnything="true" beStrictAboutTodoAnnotatedTests="true" verbose="true" defaultTimeLimit="10">
+
   <logging>
     <junit outputFile="build/phpunit/junit.xml"/>
   </logging>
diff --git a/psalm.xml b/psalm.xml
index 4e9226bd..8e1e03f6 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -5,6 +5,7 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    errorBaseline="baseline.xml"
 >
     <projectFiles>
         <directory name="src" />
diff --git a/src/LaunchDarkly/LDUser.php b/src/LaunchDarkly/LDUser.php
index 50586bfe..d49b8dd1 100644
--- a/src/LaunchDarkly/LDUser.php
+++ b/src/LaunchDarkly/LDUser.php
@@ -18,6 +18,8 @@
  * this may be a username or e-mail address. For anonymous users, it could be an IP address or session ID.
  *
  * Use {@see \LaunchDarkly\LDUserBuilder} to construct instances of this class.
+ *
+ * @deprecated Use LDContext instead.
  */
 class LDUser
 {
@@ -65,6 +67,8 @@ public function __construct(
         ?array $custom = [],
         ?array $privateAttributeNames = []
     ) {
+        trigger_error('LDUser is being removed in 6.0.0. Use LDContext instead', E_USER_DEPRECATED);
+
         $this->_key = $key;
         $this->_ip = $ip;
         $this->_country = $country;
@@ -169,7 +173,7 @@ public function getPrivateAttributeNames(): ?array
     {
         return $this->_privateAttributeNames;
     }
-    
+
     public function isKeyBlank(): bool
     {
         return empty($this->_key);
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
new file mode 100644
index 00000000..fe07e9e8
--- /dev/null
+++ b/tests/bootstrap.php
@@ -0,0 +1,5 @@
+<?php
+
+error_reporting(E_ALL & ~E_USER_DEPRECATED);
+
+require 'vendor/autoload.php';