diff --git a/gradle/changelog/jaxb_context_creation.yaml b/gradle/changelog/jaxb_context_creation.yaml
new file mode 100644
index 0000000000..d38b6b1ef0
--- /dev/null
+++ b/gradle/changelog/jaxb_context_creation.yaml
@@ -0,0 +1,2 @@
+- type: fixed
+  description: Concurrent modification exception in JAXB stores
diff --git a/scm-dao-xml/src/main/java/sonia/scm/store/TypedStoreContext.java b/scm-dao-xml/src/main/java/sonia/scm/store/TypedStoreContext.java
index 81183cd5db..f3dde1026c 100644
--- a/scm-dao-xml/src/main/java/sonia/scm/store/TypedStoreContext.java
+++ b/scm-dao-xml/src/main/java/sonia/scm/store/TypedStoreContext.java
@@ -48,8 +48,11 @@ final class TypedStoreContext<T> {
   }
 
   static <T> TypedStoreContext<T> of(TypedStoreParameters<T> parameters) {
-      JAXBContext jaxbContext = contextCache.computeIfAbsent(parameters.getType(), type -> createJaxbContext(parameters));
-      return new TypedStoreContext<>(jaxbContext, parameters);
+    JAXBContext jaxbContext;
+    synchronized (contextCache) {
+      jaxbContext = contextCache.computeIfAbsent(parameters.getType(), type -> createJaxbContext(parameters));
+    }
+    return new TypedStoreContext<>(jaxbContext, parameters);
   }
 
   private static <T> JAXBContext createJaxbContext(TypedStoreParameters<T> parameters) {