diff --git a/core/src/net/sf/openrocket/document/OpenRocketDocument.java b/core/src/net/sf/openrocket/document/OpenRocketDocument.java
index 358aca2b4..36181c8f1 100644
--- a/core/src/net/sf/openrocket/document/OpenRocketDocument.java
+++ b/core/src/net/sf/openrocket/document/OpenRocketDocument.java
@@ -34,7 +34,7 @@ import net.sf.openrocket.util.ArrayList;
  */
 public class OpenRocketDocument implements ComponentChangeListener {
 	private static final Logger log = LoggerFactory.getLogger(OpenRocketDocument.class);
-	private final List<String> file_extensions = Arrays.asList("ork", "rkt");	// Possible extensions of an OpenRocket document
+	private final List<String> file_extensions = Arrays.asList("ork", "ork.gz", "rkt", "rkt.gz");	// Possible extensions of an OpenRocket document
 	/**
 	 * The minimum number of undo levels that are stored.
 	 */
diff --git a/swing/src/net/sf/openrocket/gui/main/SaveAsFileChooser.java b/swing/src/net/sf/openrocket/gui/main/SaveAsFileChooser.java
index d6bf1427b..aba5b860e 100644
--- a/swing/src/net/sf/openrocket/gui/main/SaveAsFileChooser.java
+++ b/swing/src/net/sf/openrocket/gui/main/SaveAsFileChooser.java
@@ -41,6 +41,7 @@ public class SaveAsFileChooser extends JFileChooser {
 		switch( type ) {
 		default:
 		case OPENROCKET:
+			defaultFilename = FileHelper.forceExtension(defaultFilename,"ork");
 			this.setDialogTitle(trans.get("saveAs.openrocket.title"));
 			storageChooser = new StorageOptionChooser(document, document.getDefaultStorageOptions());
 			this.setAccessory(storageChooser);
@@ -48,6 +49,7 @@ public class SaveAsFileChooser extends JFileChooser {
 			this.setFileFilter(FileHelper.OPENROCKET_DESIGN_FILTER);
 			break;
 		case ROCKSIM:
+			defaultFilename = FileHelper.forceExtension(defaultFilename,"rkt");
 			this.setDialogTitle(trans.get("saveAs.rocksim.title"));
 			storageChooser = null;
 			this.addChoosableFileFilter(FileHelper.ROCKSIM_DESIGN_FILTER);