diff --git a/app/src/processing/app/Settings.java b/app/src/processing/app/Settings.java
index 020c20d38..b51b37570 100644
--- a/app/src/processing/app/Settings.java
+++ b/app/src/processing/app/Settings.java
@@ -94,14 +94,18 @@ public void load(File additions) {
     // check for platform-specific properties in the defaults
     String platformExt = "." + Platform.getName();
     int platformExtLength = platformExt.length();
+    HashMap<String,String> tmpMap = new HashMap<>();
     for (String key : table.keySet()) {
       if (key.endsWith(platformExt)) {
         // this is a key specific to a particular platform
         String actualKey = key.substring(0, key.length() - platformExtLength);
         String value = get(key);
-        table.put(actualKey, value);
+        //if the key is specific to this platform and is not the last property then attempting to append it to the map will throw a ConcurrentModificationException
+        //to avoid this we append it to a temporary map that can then be safely merged after the loop is complete
+        tmpMap.put(actualKey, value);
       }
     }
+    table.putAll(tmpMap);
   }
 
 
diff --git a/java/src/processing/mode/java/JavaBuild.java b/java/src/processing/mode/java/JavaBuild.java
index b367e2c8f..a76a3f819 100644
--- a/java/src/processing/mode/java/JavaBuild.java
+++ b/java/src/processing/mode/java/JavaBuild.java
@@ -735,7 +735,18 @@ protected boolean exportApplication(File destFolder,
       File resourcesFolder = new File(contentsFolder, "Resources");
       Util.copyDir(new File(contentsOrig, "Resources/en.lproj"),
                    new File(resourcesFolder, "en.lproj"));
-      Util.copyFile(mode.getContentFile("application/application.icns"),
+
+      Settings sketchProperties = new Settings(new File(sketch.getFolder(), "sketch.properties"));
+      String iconPath = sketchProperties.get("icon");//icon.macos
+      File iconFile;
+      if(iconPath == null || iconPath.isEmpty()){
+        iconFile = mode.getContentFile("application/application.icns");
+        System.out.println("using default icon");
+      }else {
+        iconFile = new File(sketch.getFolder(), iconPath);
+        System.out.println("found custom icon: "+iconPath);
+      }
+      Util.copyFile(iconFile,
                     new File(resourcesFolder, "application.icns"));
 
     } else if (exportPlatform == PConstants.LINUX) {
@@ -958,7 +969,17 @@ protected boolean exportApplication(File destFolder,
       File exeFile = new File(destFolder, sketch.getName() + ".exe");
       config.addChild("outfile").setContent(exeFile.getAbsolutePath());
 
-      File iconFile = mode.getContentFile("application/application.ico");
+      //check sketch.properties to see if an icon was set
+      Settings sketchProperties = new Settings(new File(sketch.getFolder(), "sketch.properties"));
+      String iconPath = sketchProperties.get("icon");//icon.windows
+      File iconFile;
+      if(iconPath == null || iconPath.isEmpty()){
+        iconFile = mode.getContentFile("application/application.ico");
+        System.out.println("using default icon");
+      }else {
+        iconFile = new File(sketch.getFolder(), iconPath);
+        System.out.println("found custom icon: "+iconPath);
+      }
       config.addChild("icon").setContent(iconFile.getAbsolutePath());
 
       XML clazzPath = config.addChild("classPath");