diff --git a/ABStudio/Forms/SpritesheetEditor.cs b/ABStudio/Forms/SpritesheetEditor.cs
index 789bc4f..6ff2d91 100644
--- a/ABStudio/Forms/SpritesheetEditor.cs
+++ b/ABStudio/Forms/SpritesheetEditor.cs
@@ -497,6 +497,12 @@ private void LoadBitmap(string path=null)
 
         private void RefreshZoom()
         {
+            // On some computers, this method may be called by `InitializeComponent` in the class constructor.
+            // In this case, `spritesheet` is null, which can cause NullReferenceException to be thrown.
+            // See https://github.com/giroletm/ABStudio/pull/2
+            if (spritesheet == null)
+                return;
+            
             float w = spritesheet.Width * zoom;
             float h = spritesheet.Height * zoom;