diff --git a/spring-cloud-function-context/pom.xml b/spring-cloud-function-context/pom.xml
index 9abc8837d..74273869d 100644
--- a/spring-cloud-function-context/pom.xml
+++ b/spring-cloud-function-context/pom.xml
@@ -64,12 +64,6 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-test</artifactId>
 			<optional>true</optional>
-			<exclusions>
-				<exclusion>
-					<groupId>com.vaadin.external.google</groupId>
-					<artifactId>android-json</artifactId>
-				</exclusion>
-			</exclusions>
 		</dependency>
 		<dependency>
 			<groupId>io.projectreactor</groupId>
@@ -112,12 +106,6 @@
 			<version>2.2.0</version>
 			<optional>true</optional>
 		</dependency>
-		
-		<dependency>
-		    <groupId>org.json</groupId>
-		    <artifactId>json</artifactId>
-		    <version>20240303</version>
-		</dependency>
 
 		<!-- Actuator -->
 		<dependency>
diff --git a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/json/JsonMapper.java b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/json/JsonMapper.java
index 781181fe4..4fb91f775 100644
--- a/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/json/JsonMapper.java
+++ b/spring-cloud-function-context/src/main/java/org/springframework/cloud/function/json/JsonMapper.java
@@ -24,13 +24,14 @@ import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.json.JSONArray;
-import org.json.JSONException;
-import org.json.JSONObject;
 
 import org.springframework.cloud.function.context.catalog.FunctionTypeUtils;
 
@@ -137,33 +138,33 @@ public abstract class JsonMapper {
 				&& !value.getClass().getPackage().getName().startsWith("reactor.util.function")) {
 			return true;
 		}
-		if (value instanceof byte[]) {
-			value = new String((byte[]) value, StandardCharsets.UTF_8);
+		if (value instanceof byte[] byteValue) {
+			value = new String(byteValue, StandardCharsets.UTF_8);
 		}
-		if (value instanceof String) {
+		if (value instanceof String stringValue) {
 			try {
-				new JSONArray((String) value);
+				JsonNode node = mapper.readTree(stringValue);
+				return node instanceof ArrayNode;
 			}
-			catch (JSONException e) {
+			catch (JsonProcessingException e) {
 				return false;
 			}
-			return true;
 		}
 		return false;
 	}
 
 	public static boolean isJsonStringRepresentsMap(Object value) {
-		if (value instanceof byte[]) {
-			value = new String((byte[]) value, StandardCharsets.UTF_8);
+		if (value instanceof byte[] byteValue) {
+			value = new String(byteValue, StandardCharsets.UTF_8);
 		}
-		if (value instanceof String) {
+		if (value instanceof String stringValue) {
 			try {
-				new JSONObject(value);
+				JsonNode node = mapper.readTree(stringValue);
+				return node instanceof ObjectNode;
 			}
-			catch (JSONException e) {
+			catch (JsonProcessingException e) {
 				return false;
 			}
-			return true;
 		}
 		return false;
 	}
diff --git a/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/SimpleFunctionRegistryTests.java b/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/SimpleFunctionRegistryTests.java
index 5f2fb2fb9..5c9d49c95 100644
--- a/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/SimpleFunctionRegistryTests.java
+++ b/spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/SimpleFunctionRegistryTests.java
@@ -75,6 +75,7 @@ import org.springframework.messaging.converter.AbstractMessageConverter;
 import org.springframework.messaging.converter.ByteArrayMessageConverter;
 import org.springframework.messaging.converter.CompositeMessageConverter;
 import org.springframework.messaging.converter.MessageConverter;
+import org.springframework.messaging.converter.ProtobufMessageConverter;
 import org.springframework.messaging.converter.StringMessageConverter;
 import org.springframework.messaging.support.MessageBuilder;
 import org.springframework.util.MimeType;
@@ -115,7 +116,7 @@ public class SimpleFunctionRegistryTests {
 		Function<StringValue, String> getValue = msg -> msg != null ? msg.getValue() : null;
 		Type functionType = ResolvableType.forClassWithGenerics(Function.class, ResolvableType.forClass(StringValue.class), ResolvableType.forClass(String.class)).getType();
 
-		var catalog = new SimpleFunctionRegistry(this.conversionService, this.messageConverter, new JacksonMapper(new ObjectMapper()));
+		var catalog = new SimpleFunctionRegistry(this.conversionService, new CompositeMessageConverter(List.of(new ProtobufMessageConverter())), new JacksonMapper(new ObjectMapper()));
 		catalog.register(new FunctionRegistration<>(getValue, "getValue").type(functionType));
 		FunctionInvocationWrapper lookedUpFunction = catalog.lookup("getValue");
 
@@ -129,22 +130,7 @@ public class SimpleFunctionRegistryTests {
 			.setHeader("contentType", "application/x-protobuf")
 			.build();
 
-		if (stringValue.equals("aaaaaaaaaa")) {
-			try {
-				lookedUpFunction.apply(inputMessage);
-			}
-			catch (Exception ex) {
-				assertThat(ex).isInstanceOf(ClassCastException.class);
-			}
-		}
-		else {
-			try {
-				lookedUpFunction.apply(inputMessage);
-			}
-			catch (Exception ex) {
-				assertThat(ex).isInstanceOf(IllegalStateException.class);
-			}
-		}
+		assertThat(lookedUpFunction.apply(inputMessage)).isEqualTo(stringValue);
 	}
 
 	@SuppressWarnings("rawtypes")