diff --git a/pom.xml b/pom.xml
index b9d3530..6808682 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>com.solab</groupId>
 	<artifactId>j8583</artifactId>
-	<version>1.5.0</version>
+	<version>1.5.1</version>
 	<packaging>jar</packaging>
 	<name>j8583</name>
 	<description>Java implementation of the ISO 8583 protocol, focused on making the creation, edition and reading of ISO8583 messages as simple and flexible as possible.</description>
diff --git a/src/main/java/com/solab/iso8583/IsoMessage.java b/src/main/java/com/solab/iso8583/IsoMessage.java
index acefbea..e158028 100644
--- a/src/main/java/com/solab/iso8583/IsoMessage.java
+++ b/src/main/java/com/solab/iso8583/IsoMessage.java
@@ -127,7 +127,9 @@ public class IsoMessage {
     	if (index < 2 || index > 128) {
     		throw new IndexOutOfBoundsException("Field index must be between 2 and 128");
     	}
-    	field.setCharacterEncoding(encoding);
+    	if (field != null) {
+        	field.setCharacterEncoding(encoding);
+    	}
     	fields[index] = field;
     }
 
diff --git a/src/test/java/j8583/TestIsoMessage.java b/src/test/java/j8583/TestIsoMessage.java
index 649902e..265de21 100644
--- a/src/test/java/j8583/TestIsoMessage.java
+++ b/src/test/java/j8583/TestIsoMessage.java
@@ -1,9 +1,7 @@
 package j8583;
 
-import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.UnsupportedEncodingException;
 import java.text.ParseException;
 
 import org.junit.Assert;