diff --git a/shaders/image.frag b/shaders/image.frag
index 21fdfe6..a86af41 100644
--- a/shaders/image.frag
+++ b/shaders/image.frag
@@ -34,7 +34,7 @@ void main(void)
     if(bw)color = color.rrra;
     color = MTF(color, mtf_param);
 
-    if(invert)color = vec4(1.0) - color;
+    if(invert)color.rgb = vec3(1.0) - color.rgb;
 
     color.rgb = mix(checker(), color.rgb, color.a);