diff --git a/src/lime/tools/PlatformTarget.hx b/src/lime/tools/PlatformTarget.hx
index 87cf6e1d0..fe4ea957d 100644
--- a/src/lime/tools/PlatformTarget.hx
+++ b/src/lime/tools/PlatformTarget.hx
@@ -4,6 +4,8 @@ import haxe.rtti.Meta;
 import hxp.*;
 import lime.tools.AssetHelper;
 import lime.tools.CommandHelper;
+import sys.FileSystem;
+import sys.io.File;
 
 class PlatformTarget
 {
@@ -99,10 +101,12 @@ class PlatformTarget
 		if (command == "update" || command == "build" || command == "test")
 		{
 			logCommand("update");
-			// #if lime
-			// AssetHelper.processLibraries (project, targetDirectory);
-			// #end
+
+			_touchedFiles = [];
 			update();
+
+			deleteStaleFiles(_touchedFiles);
+			_touchedFiles = null;
 		}
 
 		if (command == "build" || command == "test")
@@ -168,4 +172,85 @@ class PlatformTarget
 	@ignore public function update():Void {}
 
 	@ignore public function watch():Void {}
+
+	// Functions to track and delete stale files
+
+	/**
+		Files that were copied into the output directory due to something in
+		project.xml, but which might not be included next time.
+
+		`PlatformTarget` will handle assets and templates, but subclasses are
+		responsible for adding any other files they copy (e.g., dependencies).
+	**/
+	private var _touchedFiles:Array<String> = null;
+
+	/**
+		Calls `System.copyIfNewer()` with the given arguments, then records the
+		file in `_touchedFiles`. See `_touchedFiles` for information about what
+		needs to be recorded.
+	**/
+	private function copyIfNewer(source:String, destination:String):Void
+	{
+		System.copyIfNewer(source, destination);
+
+		if (_touchedFiles != null)
+		{
+			_touchedFiles.push(destination);
+		}
+	}
+
+	private function deleteStaleFiles(touchedFiles:Array<String>):Void
+	{
+		if (project.defines.exists("lime-ignore-stale-files")) return;
+
+		for (asset in project.assets)
+		{
+			touchedFiles.push(targetDirectory + "/bin/" + asset.targetPath);
+		}
+
+		var record:String = targetDirectory + "/.files";
+		if (FileSystem.exists(record))
+		{
+			for (oldFile in File.getContent(record).split("\n"))
+			{
+				if (oldFile.length > 0 && touchedFiles.indexOf(oldFile) < 0)
+				{
+					System.deleteFile(oldFile);
+				}
+			}
+		}
+
+		File.saveContent(record, touchedFiles.join("\n"));
+	}
+
+	/**
+		Calls `System.recursiveCopy()` with the given arguments, then records
+		the files in `_touchedFiles`. See `_touchedFiles` for information about
+		what needs to be recorded.
+	**/
+	private function recursiveCopy(source:String, destination:String, context:Dynamic = null, process:Bool = true):Void
+	{
+		System.recursiveCopy(source, destination, context, process);
+
+		if (_touchedFiles == null || !FileSystem.exists(source)) return;
+
+		function recurse(source:String, destination:String):Void
+		{
+			for (file in FileSystem.readDirectory(source))
+			{
+				if (file.charAt(0) == ".") continue;
+
+				if (FileSystem.isDirectory(source + "/" + file))
+				{
+					recurse(source + "/" + file, destination + "/" + file);
+				}
+				else
+				{
+					_touchedFiles.push(destination + "/" + file);
+				}
+			}
+		}
+
+		recurse(source, destination);
+	}
 }
diff --git a/tools/platforms/AndroidPlatform.hx b/tools/platforms/AndroidPlatform.hx
index 576f1d9fe..7ab9433bd 100644
--- a/tools/platforms/AndroidPlatform.hx
+++ b/tools/platforms/AndroidPlatform.hx
@@ -595,17 +595,17 @@ class AndroidPlatform extends PlatformTarget
 			{
 				if (FileSystem.isDirectory(javaPath))
 				{
-					System.recursiveCopy(javaPath, sourceSet + "/java", context, true);
+					recursiveCopy(javaPath, sourceSet + "/java", context, true);
 				}
 				else
 				{
 					if (Path.extension(javaPath) == "jar")
 					{
-						System.copyIfNewer(javaPath, destination + "/app/libs/" + Path.withoutDirectory(javaPath));
+						copyIfNewer(javaPath, destination + "/app/libs/" + Path.withoutDirectory(javaPath));
 					}
 					else
 					{
-						System.copyIfNewer(javaPath, sourceSet + "/java/" + Path.withoutDirectory(javaPath));
+						copyIfNewer(javaPath, sourceSet + "/java/" + Path.withoutDirectory(javaPath));
 					}
 				}
 			}
@@ -618,7 +618,7 @@ class AndroidPlatform extends PlatformTarget
 
 		for (library in cast(context.ANDROID_LIBRARY_PROJECTS, Array<Dynamic>))
 		{
-			System.recursiveCopy(library.source, destination + "/deps/" + library.name, context, true);
+			recursiveCopy(library.source, destination + "/deps/" + library.name, context, true);
 		}
 
 		ProjectHelper.recursiveSmartCopyTemplate(project, "android/template", destination, context);
diff --git a/tools/platforms/HTML5Platform.hx b/tools/platforms/HTML5Platform.hx
index 94d8a45f2..644eac2ad 100644
--- a/tools/platforms/HTML5Platform.hx
+++ b/tools/platforms/HTML5Platform.hx
@@ -438,7 +438,7 @@ class HTML5Platform extends PlatformTarget
 					var name = Path.withoutDirectory(dependency.path);
 
 					context.linkedLibraries.push("./" + dependencyPath + "/" + name);
-					System.copyIfNewer(dependency.path, Path.combine(destination, Path.combine(dependencyPath, name)));
+					copyIfNewer(dependency.path, Path.combine(destination, Path.combine(dependencyPath, name)));
 				}
 			}
 		}
diff --git a/tools/platforms/IOSPlatform.hx b/tools/platforms/IOSPlatform.hx
index dc8e9472e..e13a9cdff 100644
--- a/tools/platforms/IOSPlatform.hx
+++ b/tools/platforms/IOSPlatform.hx
@@ -862,7 +862,7 @@ class IOSPlatform extends PlatformTarget
 						fileName = "lib" + fileName;
 					}
 
-					System.copyIfNewer(dependency.path, projectDirectory + "/lib/" + arch + "/" + fileName);
+					copyIfNewer(dependency.path, projectDirectory + "/lib/" + arch + "/" + fileName);
 				}
 			}
 		}
diff --git a/tools/platforms/TVOSPlatform.hx b/tools/platforms/TVOSPlatform.hx
index e0273b3b3..76714971c 100644
--- a/tools/platforms/TVOSPlatform.hx
+++ b/tools/platforms/TVOSPlatform.hx
@@ -633,7 +633,7 @@ class TVOSPlatform extends PlatformTarget
 						fileName = "lib" + fileName;
 					}
 
-					System.copyIfNewer(dependency.path, projectDirectory + "/lib/" + arch + "/" + fileName);
+					copyIfNewer(dependency.path, projectDirectory + "/lib/" + arch + "/" + fileName);
 				}
 			}
 		}
diff --git a/tools/platforms/WebAssemblyPlatform.hx b/tools/platforms/WebAssemblyPlatform.hx
index a8130365c..0674c45b1 100644
--- a/tools/platforms/WebAssemblyPlatform.hx
+++ b/tools/platforms/WebAssemblyPlatform.hx
@@ -471,7 +471,7 @@ class WebAssemblyPlatform extends PlatformTarget
 					var name = Path.withoutDirectory(dependency.path);
 
 					context.linkedLibraries.push("./" + dependencyPath + "/" + name);
-					System.copyIfNewer(dependency.path, Path.combine(destination, Path.combine(dependencyPath, name)));
+					copyIfNewer(dependency.path, Path.combine(destination, Path.combine(dependencyPath, name)));
 				}
 			}
 		}
diff --git a/tools/platforms/WindowsPlatform.hx b/tools/platforms/WindowsPlatform.hx
index 416e5d7da..c33d2519b 100644
--- a/tools/platforms/WindowsPlatform.hx
+++ b/tools/platforms/WindowsPlatform.hx
@@ -286,7 +286,7 @@ class WindowsPlatform extends PlatformTarget
 				if (StringTools.endsWith(dependency.path, ".dll"))
 				{
 					var fileName = Path.withoutDirectory(dependency.path);
-					System.copyIfNewer(dependency.path, applicationDirectory + "/" + fileName);
+					copyIfNewer(dependency.path, applicationDirectory + "/" + fileName);
 				}
 			}
 
@@ -1121,7 +1121,7 @@ class WindowsPlatform extends PlatformTarget
 				var name = Path.withoutDirectory(dependency.path);
 
 				context.linkedLibraries.push("./js/lib/" + name);
-				System.copyIfNewer(dependency.path, Path.combine(destination, Path.combine("js/lib", name)));
+				copyIfNewer(dependency.path, Path.combine(destination, Path.combine("js/lib", name)));
 			}
 		}