diff --git a/src/main/java/org/jastadd/preprocessor/testing/plugin/RelastTest.java b/src/main/java/org/jastadd/preprocessor/testing/plugin/RelastTest.java
index e98def445a141b444434722d5e55b9efeeb2b499..3175e4e9709e27c572885e42f4e566f75c290e46 100644
--- a/src/main/java/org/jastadd/preprocessor/testing/plugin/RelastTest.java
+++ b/src/main/java/org/jastadd/preprocessor/testing/plugin/RelastTest.java
@@ -193,9 +193,12 @@ public abstract class RelastTest extends DefaultTask {
             javaExecSpec.setClasspath(runtimeClasspath);
             javaExecSpec.setMain("-jar");
             args.add(RelastTest.jastaddCompilerLocation);
-          } else {
+          } else if (RelastTest.jastaddCompilerConfiguration != null) {
             javaExecSpec.setClasspath(RelastTest.jastaddCompilerConfiguration);
             javaExecSpec.getMainClass().set("org.jastadd.JastAdd");
+          } else {
+            javaExecSpec.setClasspath(runtimeClasspath);
+            javaExecSpec.getMainClass().set("org.jastadd.JastAdd");
           }
           args.add("--o=" + pathToAbsoluteProject(getJastadd().getOutputDirOrDefault().getPath()));
           args.add("--package=" + getJastadd().getPackageName());