diff --git a/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModules.java b/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModules.java
index f4aeffd7..6fe2e8b6 100644
--- a/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModules.java
+++ b/spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModules.java
@@ -20,6 +20,7 @@ import static com.tngtech.archunit.core.domain.JavaClass.Predicates.*;
 import static java.util.stream.Collectors.*;
 
 import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -58,7 +59,7 @@ import com.tngtech.archunit.library.dependencies.SlicesRuleDefinition;
  */
 public class ApplicationModules implements Iterable<ApplicationModule> {
 
-	private static final Map<CacheKey, ApplicationModules> CACHE = new HashMap<>();
+	private static final Map<CacheKey, ApplicationModules> CACHE = new ConcurrentHashMap<>();
 	private static final ApplicationModuleDetectionStrategy DETECTION_STRATEGY;
 	private static final ImportOption IMPORT_OPTION = new ImportOption.DoNotIncludeTests();
 	private static final boolean JGRAPHT_PRESENT = ClassUtils.isPresent("org.jgrapht.Graph",
diff --git a/spring-modulith-core/src/main/java/org/springframework/modulith/core/ArchitecturallyEvidentType.java b/spring-modulith-core/src/main/java/org/springframework/modulith/core/ArchitecturallyEvidentType.java
index 2c1a6e1c..dbb6d0c8 100644
--- a/spring-modulith-core/src/main/java/org/springframework/modulith/core/ArchitecturallyEvidentType.java
+++ b/spring-modulith-core/src/main/java/org/springframework/modulith/core/ArchitecturallyEvidentType.java
@@ -20,12 +20,12 @@ import static org.springframework.modulith.core.Types.JavaXTypes.*;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Comparator;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
 
@@ -48,7 +48,7 @@ import com.tngtech.archunit.thirdparty.com.google.common.base.Suppliers;
  */
 public abstract class ArchitecturallyEvidentType {
 
-	private static Map<Key, ArchitecturallyEvidentType> CACHE = new HashMap<>();
+	private static Map<Key, ArchitecturallyEvidentType> CACHE = new ConcurrentHashMap<>();
 
 	private final JavaClass type;