diff --git a/transpiler/src/main/java/org/jsweet/transpiler/extension/RemoveJavaDependenciesAdapter.java b/transpiler/src/main/java/org/jsweet/transpiler/extension/RemoveJavaDependenciesAdapter.java
index 2c9216dc..3957a61e 100644
--- a/transpiler/src/main/java/org/jsweet/transpiler/extension/RemoveJavaDependenciesAdapter.java
+++ b/transpiler/src/main/java/org/jsweet/transpiler/extension/RemoveJavaDependenciesAdapter.java
@@ -674,14 +674,21 @@ public class RemoveJavaDependenciesAdapter extends Java2TypeScriptAdapter {
 		case "append":
 			printMacroName(targetMethodName);
 			if (invocation.getArgumentCount() == 1) {
-				print("(sb => sb.str = sb.str.concat(<any>").printArgList(invocation.getArguments()).print("))(");
+				print("(sb => { sb.str = sb.str.concat(<any>").printArgList(invocation.getArguments())
+						.print("); return sb; })(");
 				print(invocation.getTargetExpression(), delegate).print(")");
 			} else {
-				print("(sb => sb.str = sb.str.concat((<any>").print(invocation.getArgument(0)).print(").substr(")
-						.printArgList(invocation.getArgumentTail()).print(")))(");
+				print("(sb => { sb.str = sb.str.concat((<any>").print(invocation.getArgument(0)).print(").substr(")
+						.printArgList(invocation.getArgumentTail()).print(")); return sb; })(");
 				print(invocation.getTargetExpression(), delegate).print(")");
 			}
 			return true;
+		case "insert":
+			printMacroName(targetMethodName);
+			print("((sb, index, c) => { sb.str = sb.str.substr(0, index) + c + sb.str.substr(index); return sb; })(");
+			print(invocation.getTargetExpression(), delegate).print(", ").printArgList(invocation.getArguments())
+					.print(")");
+			return true;
 		case "setCharAt":
 			printMacroName(targetMethodName);
 			print("((sb, index, c) => sb.str = sb.str.substr(0, index) + c + sb.str.substr(index + 1))(");
@@ -690,13 +697,13 @@ public class RemoveJavaDependenciesAdapter extends Java2TypeScriptAdapter {
 			return true;
 		case "deleteCharAt":
 			printMacroName(targetMethodName);
-			print("((sb, index) => sb.str = sb.str.substr(0, index) + sb.str.substr(index + 1))(");
+			print("((sb, index) => { sb.str = sb.str.substr(0, index) + sb.str.substr(index + 1); return sb; })(");
 			print(invocation.getTargetExpression(), delegate).print(", ").printArgList(invocation.getArguments())
 					.print(")");
 			return true;
 		case "delete":
 			printMacroName(targetMethodName);
-			print("((sb, i1, i2) => sb.str = sb.str.substr(0, i1) + sb.str.substr(i2))(");
+			print("((sb, i1, i2) => { sb.str = sb.str.substr(0, i1) + sb.str.substr(i2); return sb; })(");
 			print(invocation.getTargetExpression(), delegate).print(", ").printArgList(invocation.getArguments())
 					.print(")");
 			return true;
diff --git a/transpiler/src/test/java/org/jsweet/test/transpiler/NativeStructuresTests.java b/transpiler/src/test/java/org/jsweet/test/transpiler/NativeStructuresTests.java
index 5a0856fd..d70ee7c2 100644
--- a/transpiler/src/test/java/org/jsweet/test/transpiler/NativeStructuresTests.java
+++ b/transpiler/src/test/java/org/jsweet/test/transpiler/NativeStructuresTests.java
@@ -50,7 +50,7 @@ public class NativeStructuresTests extends AbstractTest {
 	public void testStringBuilder() {
 		eval((logHandler, result) -> {
 			Assert.assertEquals("There should be no errors", 0, logHandler.reportedProblems.size());
-			assertEquals("a,abc,a,abc,ab,X,tEst,E,4,tst,tt", result.get("trace"));
+			assertEquals("a,abc,a,abc,ab,X,tEst,E,4,tst,tt,:qqqq,:aaaaqqqq", result.get("trace"));
 		}, getSourceFile(NativeStringBuilder.class));
 	}
 
diff --git a/transpiler/src/test/java/source/nativestructures/NativeStringBuilder.java b/transpiler/src/test/java/source/nativestructures/NativeStringBuilder.java
index fc761ca1..34589314 100644
--- a/transpiler/src/test/java/source/nativestructures/NativeStringBuilder.java
+++ b/transpiler/src/test/java/source/nativestructures/NativeStringBuilder.java
@@ -58,6 +58,14 @@ public class NativeStringBuilder {
 
 		trace.push(""+sb3);
 		
+		StringBuilder result = new StringBuilder();
+		final String variableName = "qqqq";
+		result.append(":").append(variableName);
+		trace.push(result.toString());
+
+		result.insert(1, "aaaa");
+		trace.push(result.toString());
+		
 		$export("trace", trace.join(","));
 
 	}