diff --git a/validator/src/main/java/org/mustangproject/validator/ZUGFeRDValidator.java b/validator/src/main/java/org/mustangproject/validator/ZUGFeRDValidator.java
index a07ab980..981d732f 100644
--- a/validator/src/main/java/org/mustangproject/validator/ZUGFeRDValidator.java
+++ b/validator/src/main/java/org/mustangproject/validator/ZUGFeRDValidator.java
@@ -15,6 +15,7 @@ import javax.xml.bind.annotation.adapters.HexBinaryAdapter;
 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
 
+import org.apache.commons.io.IOUtils;
 import org.dom4j.DocumentException;
 import org.dom4j.DocumentHelper;
 import org.dom4j.io.OutputFormat;
@@ -245,7 +246,7 @@ public class ZUGFeRDValidator {
 				context.addResultItem(
 					new ValidationResultItem(ESeverity.fatal, "File too small").setSection(5).setPart(EPart.pdf));
 			} else {
-				content = inputStream.readAllBytes();
+				content = IOUtils.toByteArray(inputStream);
 				isPDF = ByteArraySearcher.contains(content, new byte[]{'%', 'P', 'D', 'F'});
 				XMLValidator xv = new XMLValidator(context);
 				if (isPDF) {
diff --git a/validator/src/test/java/org/mustangproject/validator/ResourceCase.java b/validator/src/test/java/org/mustangproject/validator/ResourceCase.java
index 4149ca65..27ff2755 100644
--- a/validator/src/test/java/org/mustangproject/validator/ResourceCase.java
+++ b/validator/src/test/java/org/mustangproject/validator/ResourceCase.java
@@ -5,6 +5,7 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 
+import org.apache.commons.io.IOUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -43,7 +44,7 @@ public class ResourceCase extends TestCase {
 			if (in == null) {
 				return null;
 			}
-			return in.readAllBytes();
+			return IOUtils.toByteArray(in);
 		} catch (IOException e) {
 			LOGGER.error(e.getMessage(), e);
 			return null;