diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/ApplicationNotResponding.java b/sentry-android-core/src/main/java/io/sentry/android/core/ApplicationNotResponding.java
index 7b21c2e392c..120f2e0beff 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/ApplicationNotResponding.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/ApplicationNotResponding.java
@@ -17,6 +17,8 @@
 final class ApplicationNotResponding extends RuntimeException {
   private static final long serialVersionUID = 252541144579117016L;
 
+  // temp fix for JDK 21: Never serialized.
+  @SuppressWarnings("serial")
   private final @Nullable Thread thread;
 
   ApplicationNotResponding(final @Nullable String message) {
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/SentryUserFeedbackButton.java b/sentry-android-core/src/main/java/io/sentry/android/core/SentryUserFeedbackButton.java
index f842f18674b..589a9fa2ce6 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/SentryUserFeedbackButton.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/SentryUserFeedbackButton.java
@@ -13,6 +13,9 @@
 /**
  * @deprecated `SentryUserFeedbackButton` will be removed in the next major version
  */
+// temp fix for JDK 21: Constructors call overridable methods; making them final would break the
+// public API.
+@SuppressWarnings("this-escape")
 @Deprecated
 public class SentryUserFeedbackButton extends Button {
 
diff --git a/sentry-android-core/src/main/java/io/sentry/android/core/performance/AppStartMetrics.java b/sentry-android-core/src/main/java/io/sentry/android/core/performance/AppStartMetrics.java
index 82376a75d8b..dacab11e4f4 100644
--- a/sentry-android-core/src/main/java/io/sentry/android/core/performance/AppStartMetrics.java
+++ b/sentry-android-core/src/main/java/io/sentry/android/core/performance/AppStartMetrics.java
@@ -50,6 +50,9 @@
  * <p>This class is also responsible for - determining the app start type (cold, warm) - determining
  * if the app was launched in foreground
  */
+// temp fix for JDK 21: Constructors call overridable methods; making them final would break the
+// public API.
+@SuppressWarnings("this-escape")
 @ApiStatus.Internal
 public class AppStartMetrics extends ActivityLifecycleCallbacksAdapter {
   public interface HeadlessAppStartListener {