diff --git a/generator/src/main/java/org/sudu/protogen/generator/client/ApiMethodGeneratorBase.java b/generator/src/main/java/org/sudu/protogen/generator/client/ApiMethodGeneratorBase.java
index de4ba87..503dbde 100644
--- a/generator/src/main/java/org/sudu/protogen/generator/client/ApiMethodGeneratorBase.java
+++ b/generator/src/main/java/org/sudu/protogen/generator/client/ApiMethodGeneratorBase.java
@@ -39,12 +39,14 @@ public MethodSpec generate() {
                 .addModifiers(method.getAccessModifier())
                 .returns(returnType.getTypeName())
                 .addParameters(params)
-                .addCode(body(params))
-                .addAnnotation(
-                        method.ifNotFoundBehavior() == Options.IfNotFound.NULLIFY
-                                ? context.configuration().nullableAnnotationClass()
-                                : context.configuration().nonnullAnnotationClass()
-                );
+                .addCode(body(params));
+        if (!returnType.isPrimitiveOrVoid()) {
+            builder.addAnnotation(
+                    method.ifNotFoundBehavior() == Options.IfNotFound.NULLIFY
+                            ? context.configuration().nullableAnnotationClass()
+                            : context.configuration().nonnullAnnotationClass()
+            );
+        }
         switch (method.ifNotFoundBehavior()) {
             case NULLIFY -> builder.addAnnotation(NullifyIfNotFound.class);
             case EMPTY -> builder.addAnnotation(EmptyIfNotFound.class);
diff --git a/generator/src/main/java/org/sudu/protogen/generator/client/StubCallMethodGenerator.java b/generator/src/main/java/org/sudu/protogen/generator/client/StubCallMethodGenerator.java
index f90bd37..21bbb95 100644
--- a/generator/src/main/java/org/sudu/protogen/generator/client/StubCallMethodGenerator.java
+++ b/generator/src/main/java/org/sudu/protogen/generator/client/StubCallMethodGenerator.java
@@ -9,6 +9,7 @@
 import org.sudu.protogen.generator.type.RepeatedType;
 import org.sudu.protogen.generator.type.TypeModel;
 import org.sudu.protogen.generator.type.UnfoldedType;
+import protogen.Options;
 
 import javax.lang.model.element.Modifier;
 import java.util.List;
@@ -35,17 +36,20 @@ public StubCallMethodGenerator(GenerationContext context, Method method, TypeMod
     }
 
     public MethodSpec generate() {
-        return MethodSpec.methodBuilder(method.generatedName() + "StubCall")
+        MethodSpec.Builder builder = MethodSpec.methodBuilder(method.generatedName() + "StubCall")
                 .addModifiers(Modifier.PRIVATE)
                 .addParameters(parameters())
                 .addCode(new BodyGenerator().get())
-                .returns(returnType.getTypeName())
-                .addAnnotation(
-                        method.ifNotFoundBehavior() == NULLIFY
-                                ? context.configuration().nullableAnnotationClass()
-                                : context.configuration().nonnullAnnotationClass()
-                )
-                .build();
+                .returns(returnType.getTypeName());
+
+        if (!returnType.isPrimitiveOrVoid()) {
+            builder.addAnnotation(
+                    method.ifNotFoundBehavior() == Options.IfNotFound.NULLIFY
+                            ? context.configuration().nullableAnnotationClass()
+                            : context.configuration().nonnullAnnotationClass()
+            );
+        }
+        return builder.build();
     }
 
     private class BodyGenerator implements Supplier<CodeBlock> {
diff --git a/generator/src/main/java/org/sudu/protogen/generator/field/FieldGenerator.java b/generator/src/main/java/org/sudu/protogen/generator/field/FieldGenerator.java
index 7f04e4c..d8b8100 100644
--- a/generator/src/main/java/org/sudu/protogen/generator/field/FieldGenerator.java
+++ b/generator/src/main/java/org/sudu/protogen/generator/field/FieldGenerator.java
@@ -28,7 +28,7 @@ public FieldProcessingResult generate(Field field) {
 
         boolean isNullable = field.isNullable();
 
-        if (!type.getTypeName().isPrimitive()) {
+        if (!type.isPrimitiveOrVoid()) {
             if (field.getContainingMessage().getContainingFile().doUseNullabilityAnnotation(isNullable)) {
                 Poem.attachNullabilityAnnotations(fieldSpecBuilder, context, isNullable);
             }
diff --git a/generator/src/main/java/org/sudu/protogen/generator/server/ApiServiceMethodGenerator.java b/generator/src/main/java/org/sudu/protogen/generator/server/ApiServiceMethodGenerator.java
index 0a7037e..081a824 100644
--- a/generator/src/main/java/org/sudu/protogen/generator/server/ApiServiceMethodGenerator.java
+++ b/generator/src/main/java/org/sudu/protogen/generator/server/ApiServiceMethodGenerator.java
@@ -47,12 +47,12 @@ public MethodSpec generate() {
      * Either adds a return type or a {@code StreamObserver<Response> } parameter
      */
     private void specifyResponseWay(MethodSpec.Builder methodBuilder) {
-        TypeName returnType = responseType();
+        TypeModel returnType = responseType();
         if (method.isOutputStreaming()) {
             methodBuilder.returns(TypeName.VOID);
             methodBuilder.addParameter(generateObserverParameter(returnType));
         } else {
-            if (!returnType.isPrimitive() && method.getContainingFile().doUseNullabilityAnnotation(false)) {
+            if (!returnType.isPrimitiveOrVoid() && method.getContainingFile().doUseNullabilityAnnotation(false)) {
                 if (method.ifNotFoundBehavior() == Options.IfNotFound.NULLIFY) {
                     methodBuilder.addJavadoc("Null result is converted to Status.NOT_FOUND");
                     methodBuilder.addAnnotation(context.configuration().nullableAnnotationClass());
@@ -60,19 +60,19 @@ private void specifyResponseWay(MethodSpec.Builder methodBuilder) {
                     methodBuilder.addAnnotation(context.configuration().nonnullAnnotationClass());
                 }
             }
-            methodBuilder.returns(returnType);
+            methodBuilder.returns(returnType.getTypeName());
         }
     }
 
-    private TypeName responseType() {
+    private TypeModel responseType() {
         if (responseType != null) {
-            return responseType.getTypeName();
+            return responseType;
         }
         if (method.doUnfoldResponse(responseType)) {
             var field = method.unfoldedResponseField();
-            return context.typeManager().processType(field).getTypeName();
+            return context.typeManager().processType(field);
         }
-        return method.getOutputType().getProtobufTypeName();
+        return new TypeModel(method.getOutputType().getProtobufTypeName()); // todo make getProtobufTypeName returning TypeModel
     }
 
     private Iterable<ParameterSpec> generateRequestParameters() {
@@ -90,10 +90,10 @@ private Iterable<ParameterSpec> generateRequestParameters() {
         return List.of(ParameterSpec.builder(requestType.getTypeName(), "request").addAnnotation(NotNull.class).build());
     }
 
-    private ParameterSpec generateObserverParameter(TypeName responseType) {
+    private ParameterSpec generateObserverParameter(TypeModel responseType) {
         TypeName observerType = ParameterizedTypeName.get(
                 ClassName.get("java.util.function", "Consumer"),
-                responseType.box()
+                responseType.getTypeName().box()
         );
         return ParameterSpec.builder(observerType, "responseConsumer").addAnnotation(NotNull.class).build();
     }
diff --git a/generator/src/main/java/org/sudu/protogen/generator/type/TypeModel.java b/generator/src/main/java/org/sudu/protogen/generator/type/TypeModel.java
index 49377bf..4e73504 100644
--- a/generator/src/main/java/org/sudu/protogen/generator/type/TypeModel.java
+++ b/generator/src/main/java/org/sudu/protogen/generator/type/TypeModel.java
@@ -51,4 +51,13 @@ protected final String nextDefinition(Set<String> usedDefinitions) {
         }
         throw new IllegalStateException("Failed to define a new variable!");
     }
+
+    public boolean isPrimitiveOrVoid() {
+        return isPrimitiveOrVoid(this);
+    }
+
+    public static boolean isPrimitiveOrVoid(TypeModel typeModel) {
+        return typeModel.typeName.isPrimitive() || typeModel.typeName.equals(TypeName.VOID);
+    }
+
 }