diff --git a/src/lib.rs b/src/lib.rs
index cb4fc58..58e4313 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -122,6 +122,7 @@ impl Encoder {
             for (ComponentState { x, y, .. }, rgb) in self.factors.iter_mut() {
                 let basis = f32::cos(*x as f32 * scale_x) * f32::cos(*y as f32 * scale_y);
 
+                assert_eq!(chunk.len(), rgb.len());
                 for (val, slot) in chunk
                     .iter()
                     .map(|byte| basis * srgb_to_linear(*byte))