diff --git a/src/main/java/org/springframework/data/repository/support/ReflectionRepositoryInvoker.java b/src/main/java/org/springframework/data/repository/support/ReflectionRepositoryInvoker.java
index 38a2d4a97..93b4ee006 100644
--- a/src/main/java/org/springframework/data/repository/support/ReflectionRepositoryInvoker.java
+++ b/src/main/java/org/springframework/data/repository/support/ReflectionRepositoryInvoker.java
@@ -178,8 +178,8 @@ class ReflectionRepositoryInvoker implements RepositoryInvoker {
 	 * @see org.springframework.data.rest.core.invoke.RepositoryInvoker#invokeQueryMethod(java.lang.reflect.Method, java.util.Map, org.springframework.data.domain.Pageable, org.springframework.data.domain.Sort)
 	 */
 	@Override
-	public Optional<Object> invokeQueryMethod(Method method, MultiValueMap<String, ?> parameters,
-			Pageable pageable, Sort sort) {
+	public Optional<Object> invokeQueryMethod(Method method, MultiValueMap<String, ?> parameters, Pageable pageable,
+			Sort sort) {
 
 		Assert.notNull(method, "Method must not be null!");
 		Assert.notNull(parameters, "Parameters must not be null!");
@@ -191,8 +191,8 @@ class ReflectionRepositoryInvoker implements RepositoryInvoker {
 		return returnAsOptional(invoke(method, prepareParameters(method, parameters, pageable, sort)));
 	}
 
-	private Object[] prepareParameters(Method method, MultiValueMap<String, ?> rawParameters,
-			Pageable pageable, Sort sort) {
+	private Object[] prepareParameters(Method method, MultiValueMap<String, ?> rawParameters, Pageable pageable,
+			Sort sort) {
 
 		List<MethodParameter> parameters = new MethodParameters(method, Optional.of(PARAM_ANNOTATION)).getParameters();
 
@@ -286,6 +286,10 @@ class ReflectionRepositoryInvoker implements RepositoryInvoker {
 
 		Assert.notNull(id, "Id must not be null!");
 
+		if (idType.isInstance(id)) {
+			return id;
+		}
+
 		Object result = conversionService.convert(id, idType);
 
 		if (result == null) {
diff --git a/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java b/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java
index a2bb29c04..d453d50be 100755
--- a/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java
+++ b/src/test/java/org/springframework/data/repository/support/DomainClassConverterUnitTests.java
@@ -100,21 +100,16 @@ class DomainClassConverterUnitTests {
 		assertMatches(false);
 	}
 
-	// DATACMNS-233
+	@Test // DATACMNS-233
 	void returnsNullForNullSource() {
 		assertThat(converter.convert(null, STRING_TYPE, USER_TYPE)).isNull();
 	}
 
-	// DATACMNS-233
+	@Test // DATACMNS-233
 	void returnsNullForEmptyStringSource() {
 		assertThat(converter.convert("", STRING_TYPE, USER_TYPE)).isNull();
 	}
 
-	private void assertMatches(boolean matchExpected) {
-
-		assertThat(converter.matches(STRING_TYPE, USER_TYPE)).isEqualTo(matchExpected);
-	}
-
 	@Test
 	void convertsStringToUserCorrectly() throws Exception {
 
@@ -234,6 +229,10 @@ class DomainClassConverterUnitTests {
 		return ctx;
 	}
 
+	private void assertMatches(boolean matchExpected) {
+		assertThat(converter.matches(STRING_TYPE, USER_TYPE)).isEqualTo(matchExpected);
+	}
+
 	static interface Wrapper {
 
 		void foo(@ModelAttribute User user);