diff --git a/spring-boot-project/spring-boot-testcontainers/src/main/java/org/springframework/boot/testcontainers/lifecycle/TestcontainersLifecycleApplicationContextInitializer.java b/spring-boot-project/spring-boot-testcontainers/src/main/java/org/springframework/boot/testcontainers/lifecycle/TestcontainersLifecycleApplicationContextInitializer.java
index 4a2b52ce2c..13c40c5cc6 100644
--- a/spring-boot-project/spring-boot-testcontainers/src/main/java/org/springframework/boot/testcontainers/lifecycle/TestcontainersLifecycleApplicationContextInitializer.java
+++ b/spring-boot-project/spring-boot-testcontainers/src/main/java/org/springframework/boot/testcontainers/lifecycle/TestcontainersLifecycleApplicationContextInitializer.java
@@ -16,6 +16,8 @@
 
 package org.springframework.boot.testcontainers.lifecycle;
 
+import java.util.Collections;
+import java.util.Set;
 import java.util.WeakHashMap;
 
 import org.testcontainers.lifecycle.Startable;
@@ -34,12 +36,12 @@ import org.springframework.context.ConfigurableApplicationContext;
 public class TestcontainersLifecycleApplicationContextInitializer
 		implements ApplicationContextInitializer<ConfigurableApplicationContext> {
 
-	private static WeakHashMap<ConfigurableApplicationContext, Boolean> applied = new WeakHashMap<>();
+	private static Set<ConfigurableApplicationContext> applied = Collections.newSetFromMap(new WeakHashMap<>());
 
 	@Override
 	public void initialize(ConfigurableApplicationContext applicationContext) {
 		synchronized (applied) {
-			if (applied.put(applicationContext, Boolean.TRUE) == Boolean.TRUE) {
+			if (!applied.add(applicationContext)) {
 				return;
 			}
 		}