diff --git a/se-commons-gradle/src/main/java/de/monticore/gradle/internal/isolation/CachedIsolation.java b/se-commons-gradle/src/main/java/de/monticore/gradle/internal/isolation/CachedIsolation.java
index 55bb67d..187668d 100644
--- a/se-commons-gradle/src/main/java/de/monticore/gradle/internal/isolation/CachedIsolation.java
+++ b/se-commons-gradle/src/main/java/de/monticore/gradle/internal/isolation/CachedIsolation.java
@@ -202,7 +202,12 @@ public void executeInClassloader(String classname, String method, String[] args,
                   .getMethod(method, String[].class)
                   .invoke(null, (Object) args);
         } catch (ReflectiveOperationException e) {
-          passThrowableAlong(e.getCause());
+          if (e.getCause() == null) {
+            // some exceptions, such as ClassNotFoundExceptions, do not have a cause
+            passThrowableAlong(e);
+          } else {
+            passThrowableAlong(e.getCause());
+          }
         }
         return null;
         // Continue with the modified AccessControlContext