diff --git a/pom.xml b/pom.xml
index 7463fd9..ac9ad17 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>com.github.albfernandez</groupId>
 	<artifactId>javadbf</artifactId>
-	<version>1.2.0</version>
+	<version>1.2.1</version>
 	<url>https://github.com/albfernandez/javadbf</url>
 	<packaging>jar</packaging>
 	<name>javadbf</name>
diff --git a/src/main/java/com/linuxense/javadbf/DBFUtils.java b/src/main/java/com/linuxense/javadbf/DBFUtils.java
index 227725e..d15b3ad 100644
--- a/src/main/java/com/linuxense/javadbf/DBFUtils.java
+++ b/src/main/java/com/linuxense/javadbf/DBFUtils.java
@@ -254,10 +254,12 @@ public static boolean contains(byte[] array, byte value) {
 	 * @return true if is ascci
 	 */
 	public static boolean isPureAscii(String stringToCheck) {
-		if (stringToCheck == null) {
+		if (stringToCheck == null || stringToCheck.length() == 0) {
 			return true;
 		}
-		return ASCII_ENCODER.canEncode(stringToCheck);
+		synchronized (ASCII_ENCODER) {			
+			return ASCII_ENCODER.canEncode(stringToCheck);
+		}
 	}
 
 	/**