diff --git a/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java b/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java
index 5765b6dd3c..676ccba7d0 100644
--- a/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java
+++ b/src/ooxml/java/org/apache/poi/openxml4j/opc/OPCPackage.java
@@ -52,8 +52,8 @@ import org.apache.poi.openxml4j.opc.internal.marshallers.ZipPackagePropertiesMar
 import org.apache.poi.openxml4j.opc.internal.unmarshallers.PackagePropertiesUnmarshaller;
 import org.apache.poi.openxml4j.opc.internal.unmarshallers.UnmarshallContext;
 import org.apache.poi.openxml4j.util.Nullable;
-import org.apache.poi.util.POILogger;
 import org.apache.poi.util.POILogFactory;
+import org.apache.poi.util.POILogger;
 
 /**
  * Represents a container that can store multiple data objects.
@@ -214,9 +214,12 @@ public abstract class OPCPackage implements RelationshipSource, Closeable {
 	 */
 	public static OPCPackage open(String path, PackageAccess access)
 			throws InvalidFormatException {
-		if (path == null || "".equals(path.trim())
-				|| (new File(path).exists() && new File(path).isDirectory()))
-			throw new IllegalArgumentException("path");
+		if (path == null || "".equals(path.trim()))
+			throw new IllegalArgumentException("'path' must be given");
+		
+		File file = new File(path);
+		if (file.exists() && file.isDirectory())
+			throw new IllegalArgumentException("path must not be a directory");
 
 		OPCPackage pack = new ZipPackage(path, access);
 		if (pack.partList == null && access != PackageAccess.WRITE) {
@@ -240,8 +243,10 @@ public abstract class OPCPackage implements RelationshipSource, Closeable {
     */
    public static OPCPackage open(File file, PackageAccess access)
          throws InvalidFormatException {
-      if (file == null|| (file.exists() && file.isDirectory()))
-         throw new IllegalArgumentException("file");
+      if (file == null)
+			throw new IllegalArgumentException("'file' must be given");
+      if (file == null || (file.exists() && file.isDirectory()))
+			throw new IllegalArgumentException("file must not be a directory");
 
       OPCPackage pack = new ZipPackage(file, access);
       if (pack.partList == null && access != PackageAccess.WRITE) {
@@ -346,23 +351,21 @@ public abstract class OPCPackage implements RelationshipSource, Closeable {
 		try {
 			// Content type manager
 			pkg.contentTypeManager = new ZipContentTypeManager(null, pkg);
+			
 			// Add default content types for .xml and .rels
-			pkg.contentTypeManager
-					.addContentType(
-							PackagingURIHelper
-									.createPartName(PackagingURIHelper.PACKAGE_RELATIONSHIPS_ROOT_URI),
-							ContentTypes.RELATIONSHIPS_PART);
-			pkg.contentTypeManager
-					.addContentType(PackagingURIHelper
-							.createPartName("/default.xml"),
-							ContentTypes.PLAIN_OLD_XML);
+			pkg.contentTypeManager.addContentType(
+					PackagingURIHelper.createPartName(
+							PackagingURIHelper.PACKAGE_RELATIONSHIPS_ROOT_URI),
+					ContentTypes.RELATIONSHIPS_PART);
+			pkg.contentTypeManager.addContentType(
+					PackagingURIHelper.createPartName("/default.xml"),
+					ContentTypes.PLAIN_OLD_XML);
 
-			// Init some PackageBase properties
+			// Initialise some PackageBase properties
 			pkg.packageProperties = new PackagePropertiesPart(pkg,
 					PackagingURIHelper.CORE_PROPERTIES_PART_NAME);
-			pkg.packageProperties.setCreatorProperty("Generated by OpenXML4J");
-			pkg.packageProperties.setCreatedProperty(new Nullable<Date>(
-					new Date()));
+			pkg.packageProperties.setCreatorProperty("Generated by Apache POI OpenXML4J");
+			pkg.packageProperties.setCreatedProperty(new Nullable<Date>(new Date()));
 		} catch (InvalidFormatException e) {
 			// Should never happen
 			throw new IllegalStateException(e);