diff --git a/source/blender/compositor/realtime_compositor/shaders/compositor_keying_compute_matte.glsl b/source/blender/compositor/realtime_compositor/shaders/compositor_keying_compute_matte.glsl
index e3e6ab654ed..9f566508ed9 100644
--- a/source/blender/compositor/realtime_compositor/shaders/compositor_keying_compute_matte.glsl
+++ b/source/blender/compositor/realtime_compositor/shaders/compositor_keying_compute_matte.glsl
@@ -2,10 +2,19 @@
 #pragma BLENDER_REQUIRE(gpu_shader_common_color_utils.glsl)
 #pragma BLENDER_REQUIRE(gpu_shader_compositor_texture_utilities.glsl)
 
-float compute_saturation(vec4 color, ivec3 argmax)
+ivec3 compute_saturation_indices(vec3 v)
 {
-  float weighted_average = mix(color[argmax.y], color[argmax.z], key_balance);
-  return (color[argmax.x] - weighted_average) * abs(1.0 - weighted_average);
+  int index_of_max = ((v.x > v.y) ? ((v.x > v.z) ? 0 : 2) : ((v.y > v.z) ? 1 : 2));
+  ivec2 other_indices = ivec2(mod(ivec2(index_of_max) + ivec2(1, 2), ivec2(3)));
+  int min_index = min(other_indices.x, other_indices.y);
+  int max_index = max(other_indices.x, other_indices.y);
+  return ivec3(index_of_max, max_index, min_index);
+}
+
+float compute_saturation(vec4 color, ivec3 indices)
+{
+  float weighted_average = mix(color[indices.y], color[indices.z], key_balance);
+  return (color[indices.x] - weighted_average) * abs(1.0 - weighted_average);
 }
 
 void main()
@@ -22,9 +31,9 @@ void main()
   }
 
   vec4 key_color = texture_load(key_tx, texel);
-  ivec3 key_argmax = argmax(key_color.rgb);
-  float input_saturation = compute_saturation(input_color, key_argmax);
-  float key_saturation = compute_saturation(key_color, key_argmax);
+  ivec3 key_saturation_indices = compute_saturation_indices(key_color.rgb);
+  float input_saturation = compute_saturation(input_color, key_saturation_indices);
+  float key_saturation = compute_saturation(key_color, key_saturation_indices);
 
   float matte = 1.0f - clamp(input_saturation / key_saturation, 0.0, 1.0);