diff --git a/swing/src/net/sf/openrocket/startup/OSXSetup.java b/swing/src/net/sf/openrocket/startup/OSXSetup.java
index 8e4a0a038..3dae2435b 100644
--- a/swing/src/net/sf/openrocket/startup/OSXSetup.java
+++ b/swing/src/net/sf/openrocket/startup/OSXSetup.java
@@ -2,7 +2,6 @@ package net.sf.openrocket.startup;
 
 import java.awt.*;
 import java.awt.desktop.AboutHandler;
-import java.awt.desktop.OpenFilesEvent;
 import java.awt.desktop.OpenFilesHandler;
 import java.awt.desktop.PreferencesHandler;
 import java.awt.desktop.QuitHandler;
@@ -15,7 +14,6 @@ import net.sf.openrocket.arch.SystemInfo.Platform;
 import net.sf.openrocket.gui.dialogs.AboutDialog;
 import net.sf.openrocket.gui.dialogs.preferences.PreferencesDialog;
 import net.sf.openrocket.gui.main.BasicFrame;
-import net.sf.openrocket.gui.main.MRUDesignFile;
 
 import javax.swing.*;
 
@@ -92,7 +90,6 @@ final class OSXSetup {
 			
 			// Set handlers
 			osxDesktop.setAboutHandler(ABOUT_HANDLER);
-			osxDesktop.setOpenFileHandler(OPEN_FILE_HANDLER);
 			osxDesktop.setPreferencesHandler(PREFERENCES_HANDLER);
 			osxDesktop.setQuitHandler(QUIT_HANDLER);
 
@@ -115,4 +112,20 @@ final class OSXSetup {
 		}
 	}
 
+	/**
+	 * Sets up the open file handler, which handles file association on macOS.
+	 */
+	public static void setupOSXOpenFileHandler() {
+		if (SystemInfo.getPlatform() != Platform.MAC_OS) {
+			log.warn("Attempting to set up OSX file handler on non-MAC_OS");
+		}
+		final Desktop osxDesktop = Desktop.getDesktop();
+		if (osxDesktop == null) {
+			// Application is null: Something is wrong, give up on OS setup
+			throw new NullPointerException("com.apple.eawt.Application.getApplication() returned NULL. "
+					+ "Aborting OSX UI Setup.");
+		}
+		osxDesktop.setOpenFileHandler(OPEN_FILE_HANDLER);
+	}
+
 }
diff --git a/swing/src/net/sf/openrocket/startup/SwingStartup.java b/swing/src/net/sf/openrocket/startup/SwingStartup.java
index c95860878..5a125e702 100644
--- a/swing/src/net/sf/openrocket/startup/SwingStartup.java
+++ b/swing/src/net/sf/openrocket/startup/SwingStartup.java
@@ -85,6 +85,8 @@ public class SwingStartup {
 		SwingUtilities.invokeAndWait(new Runnable() {
 			@Override
 			public void run() {
+				// Set up the OSX file open handler here so that it can handle files that are opened when OR is not yet running.
+				OSXSetup.setupOSXOpenFileHandler();
 				runner.runInEDT(args);
 			}
 		});