diff --git a/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModule.java b/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModule.java
index 60bd60d1..50bcb1e1 100644
--- a/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModule.java
+++ b/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModule.java
@@ -968,9 +968,13 @@ public class ApplicationModule {
 
 			var originModule = getExistingModuleOf(source, modules);
 			var targetModule = getExistingModuleOf(target, modules);
+			var violations = Violations.NONE;
 
-			DeclaredDependencies declaredDependencies = originModule.getDeclaredDependencies(modules);
-			Violations violations = Violations.NONE;
+			if (originModule.equals(targetModule)) {
+				return violations;
+			}
+
+			var declaredDependencies = originModule.getDeclaredDependencies(modules);
 
 			// Check explicitly defined allowed targets
 			if (!declaredDependencies.isAllowedDependency(target)) {
diff --git a/spring-modulith-core/src/test/java/org/springframework/modulith/core/TestUtils.java b/spring-modulith-core/src/test/java/org/springframework/modulith/core/TestUtils.java
index 623557a5..c4414db2 100644
--- a/spring-modulith-core/src/test/java/org/springframework/modulith/core/TestUtils.java
+++ b/spring-modulith-core/src/test/java/org/springframework/modulith/core/TestUtils.java
@@ -17,6 +17,7 @@ package org.springframework.modulith.core;
 
 import static com.tngtech.archunit.core.domain.JavaClass.Predicates.*;
 
+import java.util.List;
 import java.util.function.Supplier;
 
 import org.jmolecules.ddd.annotation.AggregateRoot;
@@ -28,13 +29,14 @@ import com.tngtech.archunit.base.DescribedPredicate;
 import com.tngtech.archunit.core.domain.JavaClass;
 import com.tngtech.archunit.core.domain.JavaClasses;
 import com.tngtech.archunit.core.importer.ClassFileImporter;
+import com.tngtech.archunit.core.importer.ImportOption;
 
 /**
  * Utilities for testing.
  *
  * @author Oliver Drotbohm
  */
-class TestUtils {
+public class TestUtils {
 
 	private static Supplier<JavaClasses> imported = SingletonSupplier.of(() -> new ClassFileImporter() //
 			.importPackagesOf(ApplicationModules.class, Repository.class, AggregateRoot.class));
@@ -92,4 +94,9 @@ class TestUtils {
 		return Classes.of(new ClassFileImporter()
 				.importPackages(packageName));
 	}
+
+	public static ApplicationModules of(String basePackage, String... ignoredPackages) {
+		return new ApplicationModules(ModulithMetadata.of(basePackage), List.of(basePackage),
+				JavaClass.Predicates.resideInAnyPackage(ignoredPackages), false, new ImportOption.OnlyIncludeTests());
+	}
 }
diff --git a/spring-modulith-core/src/test/java/reproducers/gh660/first/Gh660Tests.java b/spring-modulith-core/src/test/java/reproducers/gh660/first/Gh660Tests.java
new file mode 100644
index 00000000..d3fb4cac
--- /dev/null
+++ b/spring-modulith-core/src/test/java/reproducers/gh660/first/Gh660Tests.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package reproducers.gh660.first;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.modulith.core.TestUtils;
+
+/**
+ * @author Oliver Drotbohm
+ */
+class Gh660Tests {
+
+	@Test // GH-660
+	void doesNotRejectInternalDependencies() {
+		TestUtils.of("reproducers.gh660").verify();
+	}
+}
diff --git a/spring-modulith-core/src/test/java/reproducers/gh660/first/package-info.java b/spring-modulith-core/src/test/java/reproducers/gh660/first/package-info.java
new file mode 100644
index 00000000..5a63dd3a
--- /dev/null
+++ b/spring-modulith-core/src/test/java/reproducers/gh660/first/package-info.java
@@ -0,0 +1,2 @@
+@org.springframework.modulith.ApplicationModule(allowedDependencies = {})
+package reproducers.gh660.first;
diff --git a/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/Product.java b/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/Product.java
new file mode 100644
index 00000000..0c18dfd6
--- /dev/null
+++ b/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/Product.java
@@ -0,0 +1,21 @@
+/*
+ * Copyright 2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package reproducers.gh660.first.repository;
+
+/**
+ * @author Oliver Drotbohm
+ */
+public class Product {}
diff --git a/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/ProductRepository.java b/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/ProductRepository.java
new file mode 100644
index 00000000..50b74f5d
--- /dev/null
+++ b/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/ProductRepository.java
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package reproducers.gh660.first.repository;
+
+/**
+ * @author Oliver Drotbohm
+ */
+public interface ProductRepository {
+	Product save(Product product);
+}
diff --git a/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/package-info.java b/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/package-info.java
new file mode 100644
index 00000000..65180dd6
--- /dev/null
+++ b/spring-modulith-core/src/test/java/reproducers/gh660/first/repository/package-info.java
@@ -0,0 +1,2 @@
+@org.springframework.modulith.NamedInterface
+package reproducers.gh660.first.repository;
diff --git a/spring-modulith-core/src/test/java/reproducers/gh660/second/ExtendingRepository.java b/spring-modulith-core/src/test/java/reproducers/gh660/second/ExtendingRepository.java
new file mode 100644
index 00000000..1f2c4ded
--- /dev/null
+++ b/spring-modulith-core/src/test/java/reproducers/gh660/second/ExtendingRepository.java
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package reproducers.gh660.second;
+
+import reproducers.gh660.first.repository.ProductRepository;
+
+/**
+ * @author Oliver Drotbohm
+ */
+public interface ExtendingRepository extends ProductRepository {}