diff --git a/src/gles_render/primitives.rs b/src/gles_render/primitives.rs
index 1f74ae8..343c022 100644
--- a/src/gles_render/primitives.rs
+++ b/src/gles_render/primitives.rs
@@ -132,7 +132,8 @@ impl GlesCanvas
 		// straight edges of pills / rounded rects. `u_size` and `u_radii`
 		// stay anchored to the original rect — `u_pad` lets the shader
 		// remap `v_uv` from the larger quad back into rect-local space.
-		let pad = 1.0_f32;
+		// Square corners take the shader's hard-edged path instead, so rects that share an edge leave no seam.
+		let pad = if corners.is_zero() { 0.0_f32 } else { 1.0 };
 		let expanded = rect.expand( pad );
 		let mvp = ortho_rect( self.width, self.height, expanded );
 		let alpha = color.a * self.global_alpha;