diff --git a/base/src/main/java/de/staropensource/sosengine/base/Engine.java b/base/src/main/java/de/staropensource/sosengine/base/Engine.java
index 9a051c5..d60bdbc 100644
--- a/base/src/main/java/de/staropensource/sosengine/base/Engine.java
+++ b/base/src/main/java/de/staropensource/sosengine/base/Engine.java
@@ -353,6 +353,7 @@ public final class Engine implements SubsystemMainClass {
      * @see DependencyVector
      * @since 1-alpha1
      */
+    @NotNull
     @Override
     public DependencyVector getDependencyVector() {
         return new DependencyVector("engine", StarOpenSourceVersioningSystem.class, EngineInformation.getVersioningString());
diff --git a/base/src/main/java/de/staropensource/sosengine/base/classes/SubsystemMainClass.java b/base/src/main/java/de/staropensource/sosengine/base/classes/SubsystemMainClass.java
index 46913de..c750935 100644
--- a/base/src/main/java/de/staropensource/sosengine/base/classes/SubsystemMainClass.java
+++ b/base/src/main/java/de/staropensource/sosengine/base/classes/SubsystemMainClass.java
@@ -24,6 +24,7 @@ import de.staropensource.sosengine.base.annotations.EventListener;
 import de.staropensource.sosengine.base.internal.events.InternalEngineShutdownEvent;
 import de.staropensource.sosengine.base.logging.LoggerInstance;
 import de.staropensource.sosengine.base.types.dependency.DependencyVector;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * The interface for engine subsystem main classes.
@@ -53,6 +54,7 @@ public interface SubsystemMainClass {
      * @see DependencyVector
      * @since 1-alpha1
      */
+    @NotNull
     DependencyVector getDependencyVector();
 
     /**
diff --git a/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java b/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java
index 668a796..4d09b08 100644
--- a/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java
+++ b/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java
@@ -36,6 +36,7 @@ import de.staropensource.sosengine.graphics.classes.ApiManagementClass;
 import de.staropensource.sosengine.graphics.events.GraphicsApiErrorEvent;
 import de.staropensource.sosengine.graphics.opengl.events.GraphicsErrorEvent;
 import lombok.Getter;
+import org.jetbrains.annotations.NotNull;
 import org.lwjgl.glfw.GLFWErrorCallback;
 import org.lwjgl.system.MemoryUtil;
 
@@ -198,6 +199,7 @@ public final class OpenGlSubsystem implements ApiMainClass {
     }
 
     /** {@inheritDoc} */
+    @NotNull
     @Override
     public DependencyVector getDependencyVector() {
         return new DependencyVector("opengl", StarOpenSourceVersioningSystem.class, EngineInformation.getVersioningString());
diff --git a/graphics/src/main/java/de/staropensource/sosengine/graphics/GraphicsSubsystem.java b/graphics/src/main/java/de/staropensource/sosengine/graphics/GraphicsSubsystem.java
index d31cd5a..8faafb6 100644
--- a/graphics/src/main/java/de/staropensource/sosengine/graphics/GraphicsSubsystem.java
+++ b/graphics/src/main/java/de/staropensource/sosengine/graphics/GraphicsSubsystem.java
@@ -148,6 +148,7 @@ public final class GraphicsSubsystem implements SubsystemMainClass {
     }
 
     /** {@inheritDoc} */
+    @NotNull
     @Override
     public DependencyVector getDependencyVector() {
         return new DependencyVector("graphics", StarOpenSourceVersioningSystem.class, EngineInformation.getVersioningString());
diff --git a/graphics/vulkan/src/main/java/de/staropensource/sosengine/graphics/vulkan/VulkanSubsystem.java b/graphics/vulkan/src/main/java/de/staropensource/sosengine/graphics/vulkan/VulkanSubsystem.java
index b02fe82..714d6c0 100644
--- a/graphics/vulkan/src/main/java/de/staropensource/sosengine/graphics/vulkan/VulkanSubsystem.java
+++ b/graphics/vulkan/src/main/java/de/staropensource/sosengine/graphics/vulkan/VulkanSubsystem.java
@@ -34,6 +34,7 @@ import de.staropensource.sosengine.graphics.classes.ApiMainClass;
 import de.staropensource.sosengine.graphics.classes.ApiManagementClass;
 import de.staropensource.sosengine.graphics.vulkan.events.GraphicsErrorEvent;
 import lombok.Getter;
+import org.jetbrains.annotations.NotNull;
 import org.lwjgl.glfw.GLFWErrorCallback;
 
 import static org.lwjgl.glfw.GLFW.*;
@@ -173,6 +174,7 @@ public final class VulkanSubsystem implements ApiMainClass {
     }
 
     /** {@inheritDoc} */
+    @NotNull
     @Override
     public DependencyVector getDependencyVector() {
         return new DependencyVector("vulkan", StarOpenSourceVersioningSystem.class, EngineInformation.getVersioningString());
diff --git a/slf4j-compat/src/main/java/de/staropensource/sosengine/slf4j_compat/Slf4jCompatibilitySubsystem.java b/slf4j-compat/src/main/java/de/staropensource/sosengine/slf4j_compat/Slf4jCompatibilitySubsystem.java
index 06446ca..28bd7c7 100644
--- a/slf4j-compat/src/main/java/de/staropensource/sosengine/slf4j_compat/Slf4jCompatibilitySubsystem.java
+++ b/slf4j-compat/src/main/java/de/staropensource/sosengine/slf4j_compat/Slf4jCompatibilitySubsystem.java
@@ -30,6 +30,7 @@ import de.staropensource.sosengine.base.types.CodePart;
 import de.staropensource.sosengine.base.types.dependency.DependencyVector;
 import de.staropensource.sosengine.base.utility.Miscellaneous;
 import lombok.Getter;
+import org.jetbrains.annotations.NotNull;
 import org.slf4j.LoggerFactory;
 
 /**
@@ -79,6 +80,7 @@ public class Slf4jCompatibilitySubsystem implements SubsystemMainClass {
     }
 
     /** {@inheritDoc} */
+    @NotNull
     @Override
     public DependencyVector getDependencyVector() {
         return new DependencyVector("slf4j-compat", StarOpenSourceVersioningSystem.class, EngineInformation.getVersioningString());