diff --git a/src/org/pEp/jniadapter/AbstractEngine.java b/src/org/pEp/jniadapter/AbstractEngine.java
index 1475aa6..66fdca0 100644
--- a/src/org/pEp/jniadapter/AbstractEngine.java
+++ b/src/org/pEp/jniadapter/AbstractEngine.java
@@ -34,6 +34,9 @@ abstract class AbstractEngine implements AutoCloseable {
     public native void stopKeyserverLookup();
 
     public static byte[] toUTF8(String str) {
+        if (str == null)
+            return null;
+
         try {
             String _str = Normalizer.normalize(str, Normalizer.Form.NFC);
             return _str.getBytes("UTF-8");
@@ -45,6 +48,9 @@ abstract class AbstractEngine implements AutoCloseable {
     }
 
     public static Vector<byte[]> toUTF8(Vector<String> list) {
+        if (list == null)
+            return null;
+
         Vector<byte[]> result = new Vector<byte[]>(list.size());
 
         for (int i=0; i<list.size(); i++)
@@ -54,6 +60,9 @@ abstract class AbstractEngine implements AutoCloseable {
     }
 
     public static Pair<byte[], byte[]> toUTF8(Pair<String, String> pair) {
+        if (pair == null)
+            return null;
+
         Pair<byte[], byte[]> result = new Pair<byte[], byte[]>();
 
         result.first = toUTF8(pair.first);
@@ -63,6 +72,9 @@ abstract class AbstractEngine implements AutoCloseable {
     }
 
     public static ArrayList<Pair<byte[], byte[]>> toUTF8(ArrayList<Pair<String, String>> list) {
+        if (list == null)
+            return null;
+
         ArrayList<Pair<byte[], byte[]>> result = new ArrayList<Pair<byte[], byte[]>>(list.size());
 
         for (int i=0; i<list.size(); i++)
@@ -72,6 +84,9 @@ abstract class AbstractEngine implements AutoCloseable {
     }
 
     public static String toUTF16(byte[] utf8) {
+        if (utf8 == null)
+            return null;
+
         try {
             return new String(utf8, "UTF-8");
         }
@@ -82,6 +97,9 @@ abstract class AbstractEngine implements AutoCloseable {
     }
 
     public static Vector<String> toUTF16(Vector<byte[]> list) {
+        if (list == null)
+            return null;
+
         Vector<String> result = new Vector<String>(list.size());
 
         for (int i=0; i<list.size(); i++)
@@ -91,6 +109,9 @@ abstract class AbstractEngine implements AutoCloseable {
     }
 
     public static Pair<String, String> toUTF16(Pair<byte[], byte[]> pair) {
+        if (pair == null)
+            return null;
+
         Pair<String, String> result = new Pair<String,String>();
 
         result.first = toUTF16(pair.first);
@@ -100,6 +121,9 @@ abstract class AbstractEngine implements AutoCloseable {
     }
 
     public static ArrayList<Pair<String, String>> toUTF16(ArrayList<Pair<byte[], byte[]>> list) {
+        if (list == null)
+            return null;
+
         ArrayList<Pair<String, String>> result = new ArrayList<Pair<String, String>>(list.size());
 
         for (int i=0; i<list.size(); i++)
diff --git a/test/Testing.java b/test/Testing.java
index be21c9d..51b420b 100644
--- a/test/Testing.java
+++ b/test/Testing.java
@@ -39,6 +39,17 @@ class Testing {
         to1.address = "vb@pep-project.org";
         to.add(to1);
         msg.setTo(to);
+
+        msg.setShortmsg("hello, world");
+        msg.setLongmsg("this is a test");
+
+        try {
+            Message enc = e.encrypt_message(msg, null);
+            System.out.println("encrypted");
+        }
+        catch (pEpException ex) {
+            System.out.println("cannot encrypt");
+        }
     }
 }