diff --git a/JavaApp/src/main/java/org/lwjgl/glfw/GLFW.java b/JavaApp/src/main/java/org/lwjgl/glfw/GLFW.java
index a08a2b2d..676e94d8 100644
--- a/JavaApp/src/main/java/org/lwjgl/glfw/GLFW.java
+++ b/JavaApp/src/main/java/org/lwjgl/glfw/GLFW.java
@@ -681,9 +681,9 @@ public class GLFW
 
     public static GLFWFramebufferSizeCallback glfwSetFramebufferSizeCallback(@NativeType("GLFWwindow *") long window, @Nullable @NativeType("GLFWframebuffersizefun") GLFWFramebufferSizeCallbackI cbfun) {
         mGLFWFramebufferSizeCallback = GLFWFramebufferSizeCallback.createSafe(nglfwSetFramebufferSizeCallback(window, memAddressSafe(cbfun)));
-        
-        mGLFWFramebufferSizeCallback.invoke(window, mGLFWWindowWidth, mGLFWWindowHeight);
-        
+        if (mGLFWFramebufferSizeCallback != null) {
+            mGLFWFramebufferSizeCallback.invoke(window, mGLFWWindowWidth, mGLFWWindowHeight);
+        }
         return mGLFWFramebufferSizeCallback;
     }
 
@@ -768,9 +768,9 @@ public class GLFW
 
     public static GLFWWindowSizeCallback glfwSetWindowSizeCallback(@NativeType("GLFWwindow *") long window, @Nullable @NativeType("GLFWwindowsizefun") GLFWWindowSizeCallbackI cbfun) {
         mGLFWWindowSizeCallback = GLFWWindowSizeCallback.createSafe(nglfwSetWindowSizeCallback(window, memAddressSafe(cbfun)));
-        
-        mGLFWWindowSizeCallback.invoke(window, mGLFWWindowWidth, mGLFWWindowHeight);
-        
+        if (mGLFWWindowSizeCallback != null) {
+            mGLFWWindowSizeCallback.invoke(window, mGLFWWindowWidth, mGLFWWindowHeight);
+        }
         return mGLFWWindowSizeCallback;
     }
     static boolean isGLFWReady;