diff --git a/src/de/inetsoftware/classparser/MethodInfo.java b/src/de/inetsoftware/classparser/MethodInfo.java
index 51910f9..9fd00d9 100644
--- a/src/de/inetsoftware/classparser/MethodInfo.java
+++ b/src/de/inetsoftware/classparser/MethodInfo.java
@@ -119,6 +119,15 @@ public class MethodInfo implements Member {
         return (accessFlags & 0x1000) > 0;
     }
 
+    /**
+     * If the method is a synthetic lambda method
+     * 
+     * @return true, if lambda method
+     */
+    public boolean isLambda() {
+        return (accessFlags & 0x1000) > 0 && name.startsWith( "lambda$" );
+    }
+
     /**
      * @return the name
      */
diff --git a/src/de/inetsoftware/jwebassembly/module/LocaleVariableManager.java b/src/de/inetsoftware/jwebassembly/module/LocaleVariableManager.java
index d5d40e8..13c139b 100644
--- a/src/de/inetsoftware/jwebassembly/module/LocaleVariableManager.java
+++ b/src/de/inetsoftware/jwebassembly/module/LocaleVariableManager.java
@@ -1,5 +1,5 @@
 /*
-   Copyright 2018 - 2020 Volker Berlin (i-net software)
+   Copyright 2018 - 2021 Volker Berlin (i-net software)
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
@@ -87,6 +87,13 @@ class LocaleVariableManager {
     void reset( LocalVariableTable variableTable, MethodInfo method, Iterator<AnyType> signature ) {
         size = 0;
 
+        if( method != null && method.isLambda() ) {
+            AnyType type = types.options.useGC() ? types.valueOf( "java/lang/Object" ) : ValueType.externref;
+            resetAddVar( type, -1 );
+            variables[0].name = "this";
+        }
+        int baseSize = size;
+
         int maxLocals;
         if( variableTable == null ) {
             maxLocals = 0;
@@ -160,7 +167,7 @@ class LocaleVariableManager {
         }
 
         // add missing slots from signature
-        if( (maxLocals > 0 || variableTable == null) && size == 0 && (method != null || signature != null )) {
+        if( (maxLocals > 0 || variableTable == null) && size == baseSize && (method != null || signature != null )) {
             Iterator<AnyType> parser = signature == null ? new ValueTypeParser( method.getType(), types ) : signature;
             if( method != null && !method.isStatic() ) {
                 resetAddVar( ValueType.externref, size );
@@ -170,12 +177,12 @@ class LocaleVariableManager {
                 if( type == null ) {
                     break;
                 }
-                resetAddVar( type, size );
+                resetAddVar( type, size - baseSize );
             }
         }
 
         // add all missing slots that we can add self temporary variables
-        NEXT: for( int i = 0; i < maxLocals; i++ ) {
+        NEXT: for( int i = 0; i < maxLocals + baseSize; i++ ) {
             for( int j = 0; j < size; j++ ) {
                 Variable var = variables[j];
                 if( var.idx == i ) {
diff --git a/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java b/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java
index 4966a7a..e27dc2b 100644
--- a/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java
+++ b/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java
@@ -224,7 +224,7 @@ public class ModuleGenerator {
                 createInstructions( functions.replace( next, method ) );
                 boolean needThisParameter = !method.isStatic()                                         // if not static there is a not declared THIS parameter
                                 || "<init>".equals( method.getName() )                                 // constructor method need also the THIS parameter also if marked as static
-                                || (method.isSynthetic() && method.getName().startsWith( "lambda$" )); // lambda functions are static but will call with a THIS parameter which need be removed from stack
+                                || (method.isLambda() );                                               // lambda functions are static but will call with a THIS parameter which need be removed from stack
                 functions.markAsScanned( next, needThisParameter );
                 if( needThisParameter ) {
                     types.valueOf( next.className ); // for the case that the type unknown yet