diff --git a/spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java b/spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java
index a7ea8c8d1f..e34d7c25ce 100644
--- a/spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java
+++ b/spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -52,6 +52,7 @@ import org.springframework.util.StringUtils;
  * @author Dave Syer
  * @author Juergen Hoeller
  * @author Sam Brannen
+ * @author Brian Clozel
  * @since 4.1
  */
 public abstract class YamlProcessor {
@@ -128,10 +129,11 @@ public abstract class YamlProcessor {
 
 	/**
 	 * Set the supported types that can be loaded from YAML documents.
-	 * <p>If no supported types are configured, all types encountered in YAML
-	 * documents will be supported. If an unsupported type is encountered, an
-	 * {@link IllegalStateException} will be thrown when the corresponding YAML
-	 * node is processed.
+	 * <p>If no supported types are configured, only Java standard classes
+	 * (as defined in {@link org.yaml.snakeyaml.constructor.SafeConstructor})
+	 * encountered in YAML documents will be supported.
+	 * If an unsupported type is encountered, an {@link IllegalStateException}
+	 * will be thrown when the corresponding YAML node is processed.
 	 * @param supportedTypes the supported types, or an empty array to clear the
 	 * supported types
 	 * @since 5.1.16
@@ -182,12 +184,8 @@ public abstract class YamlProcessor {
 	protected Yaml createYaml() {
 		LoaderOptions loaderOptions = new LoaderOptions();
 		loaderOptions.setAllowDuplicateKeys(false);
-
-		if (!this.supportedTypes.isEmpty()) {
-			return new Yaml(new FilteringConstructor(loaderOptions), new Representer(),
-					new DumperOptions(), loaderOptions);
-		}
-		return new Yaml(loaderOptions);
+		return new Yaml(new FilteringConstructor(loaderOptions), new Representer(),
+				new DumperOptions(), loaderOptions);
 	}
 
 	private boolean process(MatchCallback callback, Yaml yaml, Resource resource) {
diff --git a/spring-beans/src/test/java/org/springframework/beans/factory/config/YamlProcessorTests.java b/spring-beans/src/test/java/org/springframework/beans/factory/config/YamlProcessorTests.java
index 60fbd272ce..50c7f903a4 100644
--- a/spring-beans/src/test/java/org/springframework/beans/factory/config/YamlProcessorTests.java
+++ b/spring-beans/src/test/java/org/springframework/beans/factory/config/YamlProcessorTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,9 +17,11 @@
 package org.springframework.beans.factory.config;
 
 import java.net.URL;
+import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import org.junit.jupiter.api.Test;
 import org.yaml.snakeyaml.constructor.ConstructorException;
@@ -28,7 +30,6 @@ import org.yaml.snakeyaml.scanner.ScannerException;
 
 import org.springframework.core.io.ByteArrayResource;
 
-import static java.util.stream.Collectors.toList;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.entry;
@@ -39,10 +40,12 @@ import static org.assertj.core.api.Assertions.entry;
  * @author Dave Syer
  * @author Juergen Hoeller
  * @author Sam Brannen
+ * @author Brian Clozel
  */
 class YamlProcessorTests {
 
-	private final YamlProcessor processor = new YamlProcessor() {};
+	private final YamlProcessor processor = new YamlProcessor() {
+	};
 
 
 	@Test
@@ -79,8 +82,8 @@ class YamlProcessorTests {
 	void badResource() {
 		setYaml("foo: bar\ncd\nspam:\n  foo: baz");
 		assertThatExceptionOfType(ScannerException.class)
-			.isThrownBy(() -> this.processor.process((properties, map) -> {}))
-			.withMessageContaining("line 3, column 1");
+				.isThrownBy(() -> this.processor.process((properties, map) -> {}))
+				.withMessageContaining("line 3, column 1");
 	}
 
 	@Test
@@ -127,8 +130,8 @@ class YamlProcessorTests {
 			Map<String, Object> bar = (Map<String, Object>) map.get("bar");
 			assertThat(bar.get("spam")).isEqualTo("bucket");
 
-			List<Object> keysFromProperties = properties.keySet().stream().collect(toList());
-			List<String> keysFromFlattenedMap = flattenedMap.keySet().stream().collect(toList());
+			List<Object> keysFromProperties = new ArrayList<>(properties.keySet());
+			List<String> keysFromFlattenedMap = new ArrayList<>(flattenedMap.keySet());
 			assertThat(keysFromProperties).containsExactlyInAnyOrderElementsOf(keysFromFlattenedMap);
 			// Keys in the Properties object are sorted.
 			assertThat(keysFromProperties).containsExactly("bar.spam", "cat", "foo");
@@ -138,14 +141,23 @@ class YamlProcessorTests {
 	}
 
 	@Test
-	void customTypeSupportedByDefault() throws Exception {
+	void standardTypesSupportedByDefault() throws Exception {
+		setYaml("value: !!set\n  ? first\n  ? second");
+		this.processor.process((properties, map) -> {
+			assertThat(properties).containsExactly(entry("value[0]", "first"), entry("value[1]", "second"));
+			assertThat(map.get("value")).isInstanceOf(Set.class);
+			Set<String> set = (Set<String>) map.get("value");
+			assertThat(set).containsExactly("first", "second");
+		});
+	}
+
+	@Test
+	void customTypeNotSupportedByDefault() throws Exception {
 		URL url = new URL("https://localhost:9000/");
 		setYaml("value: !!java.net.URL [\"" + url + "\"]");
-
-		this.processor.process((properties, map) -> {
-			assertThat(properties).containsExactly(entry("value", url));
-			assertThat(map).containsExactly(entry("value", url));
-		});
+		assertThatExceptionOfType(ConstructorException.class)
+				.isThrownBy(() -> this.processor.process((properties, map) -> {}))
+				.withMessageContaining("Unsupported type encountered in YAML document: java.net.URL");
 	}
 
 	@Test
@@ -168,8 +180,8 @@ class YamlProcessorTests {
 		setYaml("value: !!java.net.URL [\"https://localhost:9000/\"]");
 
 		assertThatExceptionOfType(ConstructorException.class)
-			.isThrownBy(() -> this.processor.process((properties, map) -> {}))
-			.withMessageContaining("Unsupported type encountered in YAML document: java.net.URL");
+				.isThrownBy(() -> this.processor.process((properties, map) -> {}))
+				.withMessageContaining("Unsupported type encountered in YAML document: java.net.URL");
 	}
 
 	private void setYaml(String yaml) {