diff --git a/compiler/core/src/zserio/tools/ExtensionManager.java b/compiler/core/src/zserio/tools/ExtensionManager.java
index b7404d750..0cbf3cff0 100644
--- a/compiler/core/src/zserio/tools/ExtensionManager.java
+++ b/compiler/core/src/zserio/tools/ExtensionManager.java
@@ -153,7 +153,7 @@ private File getWorkingDirectory()
             final Path execParentPath = execPath.getParent();
             System.out.println("execParentPath = " + execParentPath);
 
-            return execParentPath.toFile();
+            return (execParentPath == null) ? null : execParentPath.toFile();
         }
         catch (SecurityException | URISyntaxException excpt)
         {