diff --git a/src/main/java/de/dhbwstuttgart/bytecode/FunNGenerator.java b/src/main/java/de/dhbwstuttgart/bytecode/FunNGenerator.java
index e5bce5f4..411d9bf2 100644
--- a/src/main/java/de/dhbwstuttgart/bytecode/FunNGenerator.java
+++ b/src/main/java/de/dhbwstuttgart/bytecode/FunNGenerator.java
@@ -28,12 +28,15 @@ public class FunNGenerator {
     private static final String objectSuperType = Type.getInternalName(Object.class).replace('.','/');
     private static final String objectSignature = applySignature(TargetType.Object);
 
+    private static final String VOID = "Ljava/lang/Void;";
+
     public static class GenericParameters {
         int start;
         public List<TargetType> parameters = new ArrayList<>();
     }
 
     private static String applyDescriptor(TargetType type, GenericParameters gep) {
+        if (type == null) return VOID;
         var res = "L" + type.getInternalName();
         if (type instanceof TargetSpecializedType a) {
             if (a.params().size() > 0) {
@@ -62,6 +65,7 @@ public class FunNGenerator {
     private static String applyNameDescriptor(TargetType a){ return a instanceof TargetGenericType ? "LTPH;" : String.format("%s", applySignature(a)); }
 
     public static String encodeType(TargetType type) {
+        if (type == null) return VOID;
         return applyNameDescriptor(type).replace("/", "$").replace(";", "$_$");
     }
 
diff --git a/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java b/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java
index cb982fa0..85feca0d 100644
--- a/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java
+++ b/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java
@@ -398,8 +398,7 @@ public class ASTToTargetAST {
 
     static TargetType flattenFunNType(List<TargetType> params, FunNGenerator.GenericParameters gep) {
         var newParams = new ArrayList<TargetType>();
-        for (var i = 0; i < params.size(); i++) {
-            var param = params.get(i);
+        for (TargetType param : params) {
             if (param instanceof TargetSpecializedType fn) {
                 collectArguments(fn, newParams);
             } else {
@@ -422,7 +421,12 @@ public class ASTToTargetAST {
                 if (name.equals("void"))
                     return null;
 
-                var params = refType.getParaList().stream().map(type -> convert(type, generics)).toList();
+                var params = refType.getParaList().stream().map(type -> {
+                    var res = convert(type, generics);
+                    if (res == null) res = new TargetRefType("java.lang.Void");
+                    return res;
+                }).toList();
+
                 if (name.matches("Fun\\d+\\$\\$")) { // TODO This seems like a bad idea
                     var className = FunNGenerator.getSpecializedClassName(FunNGenerator.getArguments(params), FunNGenerator.getReturnType(params));
                     if (!usedFunNSuperTypes.contains(params.size())) {