diff --git a/src/lime/_internal/backend/html5/HTML5Thread.hx b/src/lime/_internal/backend/html5/HTML5Thread.hx
index 022a085da..9f744e59e 100644
--- a/src/lime/_internal/backend/html5/HTML5Thread.hx
+++ b/src/lime/_internal/backend/html5/HTML5Thread.hx
@@ -96,7 +96,7 @@ class HTML5Thread {
 		var thread:HTML5Thread = new HTML5Thread(url.href, new Worker(url.href));
 
 		// Run `job` on the new thread.
-		thread.sendMessage(job);
+		thread.sendMessage(#if !haxe4 cast #end job);
 
 		return thread;
 		#else
@@ -416,7 +416,7 @@ abstract WorkFunction<T:haxe.Constraints.Function>(WorkFunctionData<T>) from Wor
 			else
 			{
 				#if !macro
-				this.sourceCode = (cast this.func:Function).toString();
+				this.sourceCode = (cast this.func #if haxe4 :Function #end).toString();
 				if (this.sourceCode.indexOf("[native code]") < 0)
 				{
 					// All set.