diff --git a/shaders/sector.gdshader b/shaders/sector.gdshader
index 67c7310b..c97f3843 100644
--- a/shaders/sector.gdshader
+++ b/shaders/sector.gdshader
@@ -28,9 +28,11 @@ vec4 sector(vec4 c, vec2 uv_pos, float r0, float r1, float w)
 }
 
 
-void rotate_vertex(inout vec2 vert, float a)
+void rotate_vec2(inout vec2 vert, float a)
 {
-    vert *= mat2(vec2(cos(a), sin(a)), vec2(-sin(a), cos(a)));
+    float sin_a = sin(a);
+    float cos_a = cos(a);
+    vert *= mat2(vec2(cos_a, sin_a), vec2(-sin_a, cos_a));
 }