diff --git a/spring-context/src/main/java/org/springframework/validation/beanvalidation/MethodValidationAdapter.java b/spring-context/src/main/java/org/springframework/validation/beanvalidation/MethodValidationAdapter.java
index fa218e5cd2..8a7f365b92 100644
--- a/spring-context/src/main/java/org/springframework/validation/beanvalidation/MethodValidationAdapter.java
+++ b/spring-context/src/main/java/org/springframework/validation/beanvalidation/MethodValidationAdapter.java
@@ -50,7 +50,6 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.ParameterNameDiscoverer;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.lang.Nullable;
-import org.springframework.util.Assert;
 import org.springframework.util.function.SingletonSupplier;
 import org.springframework.validation.BeanPropertyBindingResult;
 import org.springframework.validation.BindingResult;
@@ -321,7 +320,7 @@ public class MethodValidationAdapter implements MethodValidator {
 
 				Object arg = argumentFunction.apply(parameter.getParameterIndex());
 
-				// If the arg is a container, we need to element, but the only way to extract it
+				// If the arg is a container, we need the element, but the only way to extract it
 				// is to check for and use a container index or key on the next node:
 				// https://github.com/jakartaee/validation/issues/194
 
@@ -346,12 +345,16 @@ public class MethodValidationAdapter implements MethodValidator {
 					value = map.get(key);
 					container = map;
 				}
+				else if (arg instanceof Iterable<?>) {
+					// No index or key, cannot access the specific value
+					value = arg;
+					container = arg;
+				}
 				else if (arg instanceof Optional<?> optional) {
 					value = optional.orElse(null);
 					container = optional;
 				}
 				else {
-					Assert.state(!node.isInIterable(), "No way to unwrap Iterable without index");
 					value = arg;
 					container = null;
 				}
diff --git a/spring-context/src/test/java/org/springframework/validation/beanvalidation/MethodValidationAdapterTests.java b/spring-context/src/test/java/org/springframework/validation/beanvalidation/MethodValidationAdapterTests.java
index 0fe51acdc9..3519210f7e 100644
--- a/spring-context/src/test/java/org/springframework/validation/beanvalidation/MethodValidationAdapterTests.java
+++ b/spring-context/src/test/java/org/springframework/validation/beanvalidation/MethodValidationAdapterTests.java
@@ -19,6 +19,7 @@ package org.springframework.validation.beanvalidation;
 import java.lang.reflect.Method;
 import java.util.List;
 import java.util.Locale;
+import java.util.Set;
 import java.util.function.Consumer;
 
 import jakarta.validation.Valid;
@@ -201,9 +202,7 @@ class MethodValidationAdapterTests {
 		Method method = getMethod(target, "addHobbies");
 
 		testArgs(target, method, new Object[] {List.of("   ")}, ex -> {
-
 			assertThat(ex.getAllValidationResults()).hasSize(1);
-
 			assertValueResult(ex.getValueResults().get(0), 0, "   ", List.of("""
 				org.springframework.context.support.DefaultMessageSourceResolvable: \
 				codes [NotBlank.myService#addHobbies.hobbies,NotBlank.hobbies,NotBlank.java.util.List,NotBlank]; \
@@ -213,6 +212,22 @@ class MethodValidationAdapterTests {
 		});
 	}
 
+	@Test // gh-33150
+	void validateValueSetArgument() {
+		MyService target = new MyService();
+		Method method = getMethod(target, "addUniqueHobbies");
+
+		testArgs(target, method, new Object[] {Set.of("test", "   ")}, ex -> {
+			assertThat(ex.getAllValidationResults()).hasSize(1);
+			assertValueResult(ex.getValueResults().get(0), 0, Set.of("test", "   "), List.of("""
+				org.springframework.context.support.DefaultMessageSourceResolvable: \
+				codes [NotBlank.myService#addUniqueHobbies.hobbies,NotBlank.hobbies,NotBlank.java.util.Set,NotBlank]; \
+				arguments [org.springframework.context.support.DefaultMessageSourceResolvable: \
+				codes [myService#addUniqueHobbies.hobbies,hobbies]; \
+				arguments []; default message [hobbies]]; default message [must not be blank]"""));
+		});
+	}
+
 	private void testArgs(Object target, Method method, Object[] args, Consumer<MethodValidationResult> consumer) {
 		consumer.accept(this.validationAdapter.validateArguments(target, method, null, args, new Class<?>[0]));
 	}
@@ -271,6 +286,8 @@ class MethodValidationAdapterTests {
 		public void addHobbies(List<@NotBlank String> hobbies) {
 		}
 
+		public void addUniqueHobbies(Set<@NotBlank String> hobbies) {
+		}
 	}