diff --git a/sway/desktop/fx_renderer.c b/sway/desktop/fx_renderer.c
index 90601351..abc6d934 100644
--- a/sway/desktop/fx_renderer.c
+++ b/sway/desktop/fx_renderer.c
@@ -625,8 +625,7 @@ void fx_render_box_shadow(struct fx_renderer *renderer, const struct wlr_box *bo
 	glUseProgram(renderer->shaders.box_shadow.program);
 
 	glUniformMatrix3fv(renderer->shaders.box_shadow.proj, 1, GL_FALSE, gl_matrix);
-	glUniform3f(renderer->shaders.box_shadow.color, color[0], color[1], color[2]);
-	glUniform1f(renderer->shaders.box_shadow.alpha, color[3]);
+	glUniform4f(renderer->shaders.box_shadow.color, color[0], color[1], color[2], color[3]);
 	glUniform1f(renderer->shaders.box_shadow.blur_sigma, blur_sigma);
 	glUniform1f(renderer->shaders.box_shadow.corner_radius, corner_radius);
 
diff --git a/sway/desktop/shaders/box_shadow.frag b/sway/desktop/shaders/box_shadow.frag
index be385742..c9b2b91f 100644
--- a/sway/desktop/shaders/box_shadow.frag
+++ b/sway/desktop/shaders/box_shadow.frag
@@ -1,9 +1,9 @@
 // Writeup: https://madebyevan.com/shaders/fast-rounded-rectangle-shadows/
 
 precision mediump float;
+varying vec4 v_color;
 varying vec2 v_texcoord;
 
-uniform vec3 color;
 uniform vec2 position;
 uniform vec2 size;
 uniform float blur_sigma;
@@ -70,6 +70,5 @@ void main() {
     // dither the alpha to break up color bands
     frag_alpha += (random() - 0.5) / 128.0;
 
-    gl_FragColor = vec4(color, frag_alpha);
+    gl_FragColor = vec4(v_color.rgb, frag_alpha);
 }
-