diff --git a/tools/src/main/java/io/toolisticon/aptk/tools/generators/FileObjectSimpleWriter.java b/tools/src/main/java/io/toolisticon/aptk/tools/generators/FileObjectSimpleWriter.java
index c286be68..47212d2e 100644
--- a/tools/src/main/java/io/toolisticon/aptk/tools/generators/FileObjectSimpleWriter.java
+++ b/tools/src/main/java/io/toolisticon/aptk/tools/generators/FileObjectSimpleWriter.java
@@ -10,7 +10,7 @@
 /**
  * Abstract base class for writers of java code and resources.
  */
-public class FileObjectSimpleWriter<T extends FileObject> extends SimpleWriter{
+public class FileObjectSimpleWriter<T extends FileObject> extends SimpleWriter implements AutoCloseable{
 
     private final T fileObject;
     private final Writer foWriter;
diff --git a/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleKotlinWriter.java b/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleKotlinWriter.java
index 9379efe4..2785b208 100644
--- a/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleKotlinWriter.java
+++ b/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleKotlinWriter.java
@@ -15,7 +15,7 @@
 /**
  * A simple writer for writing kotlin source files.
  */
-public class SimpleKotlinWriter extends SimpleWriter {
+public class SimpleKotlinWriter extends SimpleWriter implements AutoCloseable{
 
     final static String KAPT_KOTLIN_GENERATED = "kapt.kotlin.generated";
     private final static Pattern PACKAGE_PATTERN = Pattern.compile("(\\w+?(?:[.]\\w+?)*)[.]\\w*");
diff --git a/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleResourceReader.java b/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleResourceReader.java
index 8379b649..ffdbb793 100644
--- a/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleResourceReader.java
+++ b/tools/src/main/java/io/toolisticon/aptk/tools/generators/SimpleResourceReader.java
@@ -11,7 +11,7 @@
 /**
  * Simple helper class to open and read a resource file.
  */
-public class SimpleResourceReader {
+public class SimpleResourceReader implements AutoCloseable{
 
     private final FileObject fileObject;
     private final BufferedReader foReader;